diff --git a/eek/eek-gtk-keyboard.c b/eek/eek-gtk-keyboard.c
index 94e7531d..1531f4ec 100644
--- a/eek/eek-gtk-keyboard.c
+++ b/eek/eek-gtk-keyboard.c
@@ -99,8 +99,7 @@ eek_gtk_keyboard_real_draw (GtkWidget *self,
         eek_renderer_set_scale_factor (priv->renderer,
                                        gtk_widget_get_scale_factor (self));
     }
-
-    eek_renderer_render_keyboard (priv->renderer, cr);
+    eek_renderer_render_keyboard (priv->renderer, priv->submission, cr);
     return FALSE;
 }
 
diff --git a/eek/eek-renderer.c b/eek/eek-renderer.c
index 45ff5cd5..c8d03e48 100644
--- a/eek/eek-renderer.c
+++ b/eek/eek-renderer.c
@@ -214,8 +214,10 @@ render_button_label (cairo_t     *cr,
     g_object_unref (layout);
 }
 
+// FIXME: Pass just the active modifiers instead of entire submission
 void
 eek_renderer_render_keyboard (EekRenderer *self,
+                              struct submission *submission,
                                    cairo_t     *cr)
 {
     EekRendererPrivate *priv = eek_renderer_get_instance_private (self);
@@ -235,7 +237,7 @@ eek_renderer_render_keyboard (EekRenderer *self,
     cairo_scale (cr, priv->widget_to_layout.scale, priv->widget_to_layout.scale);
 
     squeek_draw_layout_base_view(priv->keyboard->layout, self, cr);
-    squeek_layout_draw_all_changed(priv->keyboard->layout, self, cr);
+    squeek_layout_draw_all_changed(priv->keyboard->layout, self, cr, submission);
     cairo_restore (cr);
 }
 
diff --git a/eek/eek-renderer.h b/eek/eek-renderer.h
index 0d46237e..954ad171 100644
--- a/eek/eek-renderer.h
+++ b/eek/eek-renderer.h
@@ -25,6 +25,7 @@
 #include <pango/pangocairo.h>
 
 #include "eek-types.h"
+#include "src/submission.h"
 
 G_BEGIN_DECLS
 
@@ -59,7 +60,7 @@ cairo_surface_t *eek_renderer_get_icon_surface(const gchar     *icon_name,
                                                 gint             size,
                                                 gint             scale);
 
-void             eek_renderer_render_keyboard  (EekRenderer     *renderer,
+void             eek_renderer_render_keyboard  (EekRenderer     *renderer, struct submission *submission,
                                                 cairo_t         *cr);
 
 struct transformation
diff --git a/src/action.rs b/src/action.rs
index b356a038..693dd1c5 100644
--- a/src/action.rs
+++ b/src/action.rs
@@ -10,8 +10,11 @@ pub struct KeySym(pub String);
 type View = String;
 
 /// Use to send modified keypresses
-#[derive(Debug, Clone, PartialEq)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum Modifier {
+    /// Control and Alt are the only modifiers
+    /// which doesn't interfere with levels,
+    /// so it's simple to implement as levels are deprecated in squeekboard.
     Control,
     Alt,
 }
@@ -27,8 +30,8 @@ pub enum Action {
         /// When unlocked by pressing it or emitting a key
         unlock: View,
     },
-    /// Set this modifier TODO: release?
-    SetModifier(Modifier),
+    /// Hold this modifier for as long as the button is pressed
+    ApplyModifier(Modifier),
     /// Submit some text
     Submit {
         /// Text to submit with input-method.
diff --git a/src/data.rs b/src/data.rs
index effa7981..163b7b30 100644
--- a/src/data.rs
+++ b/src/data.rs
@@ -240,14 +240,20 @@ type ButtonIds = String;
 #[derive(Debug, Default, Deserialize, PartialEq)]
 #[serde(deny_unknown_fields)]
 struct ButtonMeta {
-    /// Special action to perform on activation. Conflicts with keysym, text.
+    // TODO: structure (action, keysym, text, modifier) as an enum
+    // to detect conflicts and missing values at compile time
+    /// Special action to perform on activation.
+    /// Conflicts with keysym, text, modifier.
     action: Option<Action>,
     /// The name of the XKB keysym to emit on activation.
-    /// Conflicts with action, text
+    /// Conflicts with action, text, modifier.
     keysym: Option<String>,
     /// The text to submit on activation. Will be derived from ID if not present
-    /// Conflicts with action, keysym
+    /// Conflicts with action, keysym, modifier.
     text: Option<String>,
+    /// The modifier to apply while the key is locked
+    /// Conflicts with action, keysym, text
+    modifier: Option<Modifier>,
     /// If not present, will be derived from text or the button ID
     label: Option<String>,
     /// Conflicts with label
@@ -270,6 +276,20 @@ enum Action {
     Erase,
 }
 
+#[derive(Debug, Clone, PartialEq, Deserialize)]
+#[serde(deny_unknown_fields)]
+enum Modifier {
+    Control,
+    Shift,
+    Lock,
+    #[serde(alias="Mod1")]
+    Alt,
+    Mod2,
+    Mod3,
+    Mod4,
+    Mod5,
+}
+
 #[derive(Debug, Clone, Deserialize, PartialEq)]
 #[serde(deny_unknown_fields)]
 struct Outline {
@@ -510,22 +530,27 @@ fn create_action<H: logging::Handler>(
         Action(Action),
         Text(String),
         Keysym(String),
+        Modifier(Modifier),
     };
     
     let submission = match (
         &symbol_meta.action,
         &symbol_meta.keysym,
-        &symbol_meta.text
+        &symbol_meta.text,
+        &symbol_meta.modifier,
     ) {
-        (Some(action), None, None) => SubmitData::Action(action.clone()),
-        (None, Some(keysym), None) => SubmitData::Keysym(keysym.clone()),
-        (None, None, Some(text)) => SubmitData::Text(text.clone()),
-        (None, None, None) => SubmitData::Text(name.into()),
+        (Some(action), None, None, None) => SubmitData::Action(action.clone()),
+        (None, Some(keysym), None, None) => SubmitData::Keysym(keysym.clone()),
+        (None, None, Some(text), None) => SubmitData::Text(text.clone()),
+        (None, None, None, Some(modifier)) => {
+            SubmitData::Modifier(modifier.clone())
+        },
+        (None, None, None, None) => SubmitData::Text(name.into()),
         _ => {
             warning_handler.handle(
                 logging::Level::Warning,
                 &format!(
-                    "Button {} has more than one of (action, keysym, text)",
+                    "Button {} has more than one of (action, keysym, text, modifier)",
                     name,
                 ),
             );
@@ -614,6 +639,26 @@ fn create_action<H: logging::Handler>(
                 })
             }).collect(),
         },
+        SubmitData::Modifier(modifier) => match modifier {
+            Modifier::Control => action::Action::ApplyModifier(
+                action::Modifier::Control,
+            ),
+            Modifier::Alt => action::Action::ApplyModifier(
+                action::Modifier::Alt,
+            ),
+            unsupported_modifier => {
+                warning_handler.handle(
+                    logging::Level::Bug,
+                    &format!(
+                        "Modifier {:?} unsupported", unsupported_modifier,
+                    ),
+                );
+                action::Action::Submit {
+                    text: None,
+                    keys: Vec::new(),
+                }
+            },
+        },
     }
 }
 
@@ -711,6 +756,7 @@ mod tests {
                         keysym: None,
                         action: None,
                         text: None,
+                        modifier: None,
                         label: Some("test".into()),
                         outline: None,
                     }
@@ -852,6 +898,7 @@ mod tests {
                         keysym: None,
                         text: None,
                         action: None,
+                        modifier: None,
                         label: Some("test".into()),
                         outline: None,
                     }
diff --git a/src/drawing.rs b/src/drawing.rs
index 504b6ec2..5a0f91ad 100644
--- a/src/drawing.rs
+++ b/src/drawing.rs
@@ -3,9 +3,11 @@
 use cairo;
 use std::cell::RefCell;
 
+use ::action::Action;
 use ::keyboard;
 use ::layout::{ Button, Layout };
 use ::layout::c::{ EekGtkKeyboard, Point };
+use ::submission::Submission;
 
 use glib::translate::FromGlibPtrNone;
 use gtk::WidgetExt;
@@ -44,13 +46,21 @@ mod c {
         layout: *mut Layout,
         renderer: EekRenderer,
         cr: *mut cairo_sys::cairo_t,
+        submission: *const Submission,
     ) {
         let layout = unsafe { &mut *layout };
+        let submission = unsafe { &*submission };
         let cr = unsafe { cairo::Context::from_raw_none(cr) };
+        let active_modifiers = submission.get_active_modifiers();
 
         layout.foreach_visible_button(|offset, button| {
             let state = RefCell::borrow(&button.state).clone();
-            let locked = state.action.is_active(&layout.current_view);
+            let active_mod = match &state.action {
+                Action::ApplyModifier(m) => active_modifiers.contains(m),
+                _ => false,
+            };
+            let locked = state.action.is_active(&layout.current_view)
+                | active_mod;
             if state.pressed == keyboard::PressType::Pressed || locked {
                 render_button_at_position(
                     renderer, &cr,
diff --git a/src/keyboard.rs b/src/keyboard.rs
index b1600fba..aefc4c6e 100644
--- a/src/keyboard.rs
+++ b/src/keyboard.rs
@@ -23,6 +23,24 @@ pub enum PressType {
 
 pub type KeyCode = u32;
 
+bitflags!{
+    /// Map to `virtual_keyboard.modifiers` modifiers values
+    /// From https://www.x.org/releases/current/doc/kbproto/xkbproto.html#Keyboard_State
+    pub struct Modifiers: u8 {
+        const SHIFT = 0x1;
+        const LOCK = 0x2;
+        const CONTROL = 0x4;
+        /// Alt
+        const MOD1 = 0x8;
+        const MOD2 = 0x10;
+        const MOD3 = 0x20;
+        /// Meta
+        const MOD4 = 0x40;
+        /// AltGr
+        const MOD5 = 0x80;
+    }
+}
+
 /// When the submitted actions of keys need to be tracked,
 /// they need a stable, comparable ID
 #[derive(PartialEq)]
diff --git a/src/layout.h b/src/layout.h
index eefcce36..cd00d128 100644
--- a/src/layout.h
+++ b/src/layout.h
@@ -7,6 +7,7 @@
 #include "eek/eek-gtk-keyboard.h"
 #include "eek/eek-renderer.h"
 #include "eek/eek-types.h"
+#include "src/submission.h"
 #include "virtual-keyboard-unstable-v1-client-protocol.h"
 
 enum squeek_arrangement_kind {
@@ -53,6 +54,6 @@ void squeek_layout_drag(struct squeek_layout *layout,
                         struct transformation widget_to_layout,
                         uint32_t timestamp, EekboardContextService *manager,
                         EekGtkKeyboard *ui_keyboard);
-void squeek_layout_draw_all_changed(struct squeek_layout *layout, EekRenderer* renderer, cairo_t     *cr);
+void squeek_layout_draw_all_changed(struct squeek_layout *layout, EekRenderer* renderer, cairo_t     *cr, struct submission *submission);
 void squeek_draw_layout_base_view(struct squeek_layout *layout, EekRenderer* renderer, cairo_t     *cr);
 #endif
diff --git a/src/layout.rs b/src/layout.rs
index 12227ef5..09fc4f72 100644
--- a/src/layout.rs
+++ b/src/layout.rs
@@ -990,6 +990,18 @@ mod seat {
                     )
                     .apply()
             },
+            Action::ApplyModifier(modifier) => {
+                // FIXME: key id is unneeded with stateless locks
+                let key_id = KeyState::get_id(rckey);
+                let gets_locked = !submission.is_modifier_active(modifier.clone());
+                match gets_locked {
+                    true => submission.handle_add_modifier(
+                        key_id,
+                        modifier, time,
+                    ),
+                    false => submission.handle_drop_modifier(key_id, time),
+                }
+            }
             // only show when UI is present
             Action::ShowPreferences => if let Some(ui) = &ui {
                 // only show when layout manager is available
@@ -1016,10 +1028,6 @@ mod seat {
                     }
                 }
             },
-            Action::SetModifier(_) => log_print!(
-                logging::Level::Bug,
-                "Modifiers unsupported",
-            ),
         };
 
         let pointer = ::util::Pointer(rckey.clone());
diff --git a/src/submission.rs b/src/submission.rs
index e681b2e3..a98d1c18 100644
--- a/src/submission.rs
+++ b/src/submission.rs
@@ -16,14 +16,19 @@
  * The text-input interface may be enabled and disabled at arbitrary times,
  * and those events SHOULD NOT cause any lost events.
  * */
- 
+
+use std::collections::HashSet;
 use std::ffi::CString;
- 
+use ::action::Modifier;
 use ::imservice;
 use ::imservice::IMService;
-use ::keyboard::{ KeyCode, KeyStateId, PressType };
+use ::keyboard::{ KeyCode, KeyStateId, Modifiers, PressType };
+use ::util::vec_remove;
 use ::vkeyboard::VirtualKeyboard;
 
+// traits
+use std::iter::FromIterator;
+
 /// Gathers stuff defined in C or called by C
 pub mod c {
     use super::*;
@@ -60,6 +65,7 @@ pub mod c {
         Box::<Submission>::into_raw(Box::new(
             Submission {
                 imservice,
+                modifiers_active: Vec::new(),
                 virtual_keyboard: VirtualKeyboard(vk),
                 pressed: Vec::new(),
             }
@@ -106,6 +112,7 @@ enum SubmittedAction {
 pub struct Submission {
     imservice: Option<Box<IMService>>,
     virtual_keyboard: VirtualKeyboard,
+    modifiers_active: Vec<(KeyStateId, Modifier)>,
     pressed: Vec<(KeyStateId, SubmittedAction)>,
 }
 
@@ -125,8 +132,10 @@ impl Submission {
         keycodes: &Vec<KeyCode>,
         time: Timestamp,
     ) {
-        let was_committed_as_text = match &mut self.imservice {
-            Some(imservice) => {
+        let mods_are_on = !self.modifiers_active.is_empty();
+
+        let was_committed_as_text = match (&mut self.imservice, mods_are_on) {
+            (Some(imservice), false) => {
                 enum Outcome {
                     Submitted(Result<(), imservice::SubmitError>),
                     NotSubmitted,
@@ -157,7 +166,7 @@ impl Submission {
                     Outcome::NotSubmitted => false,
                 }
             },
-            _ => false,
+            (_, _) => false,
         };
 
         let submit_action = match was_committed_as_text {
@@ -194,4 +203,44 @@ impl Submission {
             }
         };
     }
+    
+    pub fn handle_add_modifier(
+        &mut self,
+        key_id: KeyStateId,
+        modifier: Modifier, _time: Timestamp,
+    ) {
+        self.modifiers_active.push((key_id, modifier));
+        self.update_modifiers();
+    }
+
+    pub fn handle_drop_modifier(
+        &mut self,
+        key_id: KeyStateId,
+        _time: Timestamp,
+    ) {
+        vec_remove(&mut self.modifiers_active, |(id, _)| *id == key_id);
+        self.update_modifiers();
+    }
+
+    fn update_modifiers(&mut self) {
+        let raw_modifiers = self.modifiers_active.iter()
+            .map(|(_id, m)| match m {
+                Modifier::Control => Modifiers::CONTROL,
+                Modifier::Alt => Modifiers::MOD1,
+            })
+            .fold(Modifiers::empty(), |m, n| m | n);
+        self.virtual_keyboard.set_modifiers_state(raw_modifiers);
+    }
+
+    pub fn is_modifier_active(&self, modifier: Modifier) -> bool {
+        self.modifiers_active.iter()
+            .position(|(_id, m)| *m == modifier)
+            .is_some()
+    }
+
+    pub fn get_active_modifiers(&self) -> HashSet<Modifier> {
+        HashSet::from_iter(
+            self.modifiers_active.iter().map(|(_id, m)| m.clone())
+        )
+    }
 }
diff --git a/src/util.rs b/src/util.rs
index d58a3e77..9dafb34e 100644
--- a/src/util.rs
+++ b/src/util.rs
@@ -195,6 +195,12 @@ pub trait WarningHandler {
     fn handle(&mut self, warning: &str);
 }
 
+/// Removes the first matcing item
+pub fn vec_remove<T, F: FnMut(&T) -> bool>(v: &mut Vec<T>, pred: F) -> Option<T> {
+    let idx = v.iter().position(pred);
+    idx.map(|idx| v.remove(idx))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/src/vkeyboard.rs b/src/vkeyboard.rs
index aac5d18f..d3e086e7 100644
--- a/src/vkeyboard.rs
+++ b/src/vkeyboard.rs
@@ -1,6 +1,6 @@
 /*! Managing the events belonging to virtual-keyboard interface. */
 
-use ::keyboard::{ KeyCode, PressType };
+use ::keyboard::{ KeyCode, Modifiers, PressType };
 use ::layout::c::LevelKeyboard;
 use ::submission::Timestamp;
 
@@ -26,6 +26,11 @@ pub mod c {
             virtual_keyboard: ZwpVirtualKeyboardV1,
             keyboard: LevelKeyboard,
         );
+        
+        pub fn eek_virtual_keyboard_set_modifiers(
+            virtual_keyboard: ZwpVirtualKeyboardV1,
+            modifiers: u32,
+        );
     }
 }
 
@@ -33,7 +38,7 @@ pub mod c {
 pub struct VirtualKeyboard(pub c::ZwpVirtualKeyboardV1);
 
 impl VirtualKeyboard {
-    // TODO: split out keyboard state management
+    // TODO: error out if keymap not set
     pub fn switch(
         &self,
         keycodes: &Vec<KeyCode>,
@@ -68,12 +73,16 @@ impl VirtualKeyboard {
         }
     }
     
+    pub fn set_modifiers_state(&self, modifiers: Modifiers) {
+        let modifiers = modifiers.bits() as u32;
+        unsafe {
+            c::eek_virtual_keyboard_set_modifiers(self.0, modifiers);
+        }
+    }
+    
     pub fn update_keymap(&self, keyboard: LevelKeyboard) {
         unsafe {
-            c::eek_virtual_keyboard_update_keymap(
-                self.0,
-                keyboard,
-            );
+            c::eek_virtual_keyboard_update_keymap(self.0, keyboard);
         }
     }
 }
diff --git a/src/wayland.c b/src/wayland.c
index 42ba59df..a0f7e7b7 100644
--- a/src/wayland.c
+++ b/src/wayland.c
@@ -20,6 +20,12 @@ void eek_virtual_keyboard_update_keymap(struct zwp_virtual_keyboard_v1 *zwp_virt
         keyboard->keymap_fd, keyboard->keymap_len);
 }
 
+void
+eek_virtual_keyboard_set_modifiers(struct zwp_virtual_keyboard_v1 *zwp_virtual_keyboard_v1, uint32_t mods_depressed) {
+    zwp_virtual_keyboard_v1_modifiers(zwp_virtual_keyboard_v1,
+                                      mods_depressed, 0, 0, 0);
+}
+
 int squeek_output_add_listener(struct wl_output *wl_output,
                                 const struct wl_output_listener *listener, void *data) {
     return wl_output_add_listener(wl_output, listener, data);