diff --git a/src/common.scad b/src/common.scad
index 5113437..a80f0e7 100644
--- a/src/common.scad
+++ b/src/common.scad
@@ -9,3 +9,5 @@ module cubi(s, fillet=0, edges=EDGES_ALL) {
     }
 }
 
+function vec_sum(v, w) = [v.x + w.x, v.y + w.y, v.z + w.z];
+
diff --git a/src/harness.scad b/src/harness.scad
index 97c39ed..084c6f8 100644
--- a/src/harness.scad
+++ b/src/harness.scad
@@ -395,7 +395,7 @@ module phone_harness() {
 }
 
 module model() {
-    up(get_platform_size().z + get_harness_size().z/2) phone_harness();
+    up(get_harness_size().z/2) phone_harness();
 }
 
 if (!is_undef(validation)) {
diff --git a/src/platform.scad b/src/platform.scad
index 95ae8d8..cb368cc 100644
--- a/src/platform.scad
+++ b/src/platform.scad
@@ -1,4 +1,6 @@
 include <export.scad>
+//export=MODEL_PLATFORM_HARNESS;
+//export=MODEL_PLATFORM_STRAP;
 
 // dependency: https://github.com/revarbat/BOSL
 include <BOSL/constants.scad>
@@ -10,6 +12,7 @@ use <BOSL/sliders.scad>
 use <specs_platform.scad>
 use <specs_strap.scad>
 
+use <common.scad>
 use <strap_common.scad>
 use <platform_common.scad>
 
@@ -33,21 +36,109 @@ module model_prop_arm() {
 // <<<
 
 // Blocks:
+module lock_pin(groove) {
+    slack=groove
+        ?[1, 0.5, 0.3]
+        :[0, 0, 0];
+    pin_size=get_platform_lock_pin_size();
+    size=vec_sum(pin_size, slack);
+    down(size.z/2)
+    translate([slack.x/2, slack.y/2, slack.z/2])
+    xrot(-4) zrot(-90) right_triangle([size.y, size.x, size.z]);
+}
+module lock_arm() {
+    size=get_platform_lock_arm_size();
+    down(get_platform_top_size().z) back(size.y/2) right(size.x/2) cube(size, center=true);
+    joiner_size=[get_platform_lock_pin_size().x, size.y, get_platform_top_size().z];
+    translate([joiner_size.x/2, joiner_size.y/2, -joiner_size.z/2 + size.z/2]) cube(joiner_size, center=true);
+}
+module lock_mechanism_button(groove=false) {
+    button_size=groove
+        ?[10,5]
+        :[7,4.5];
+    size=[button_size.x, get_platform_wall()*7, button_size.y];
+    translate([get_platform_lock_pin_size().x*1.5, -get_platform_size().y/2+size.y*1.3, -get_platform_size().z/2])
+    cube(size, center=true);
+}
+module lock_buttons_cutout() {
+    module cutout_side(groove) {
+        translate(get_platform_lock_pin_pos()) lock_mechanism_button(groove=true);
+    }
+    cutout_side();
+    scale([1, -1, 1]) cutout_side();
+}
+module lock_mechanism() {
+    lock_pin(groove=false);
+    lock_arm();
+    lock_mechanism_button();
+}
+module lock_socket() {
+    pin_size=get_platform_lock_pin_size();
+    size=[pin_size.x, pin_size.y, pin_size.z];
+    module socket_connector() {
+        conn_size=[pin_size.x+4, get_platform_wall()*3, get_platform_top_size().z];
+        up(pin_size.z/2) fwd(pin_size.y+conn_size.y/2) right(pin_size.x/2) {
+            prismoid(size1=[conn_size.x, conn_size.y], size2=[conn_size.x, conn_size.y-2], shift=[0, -1], h=conn_size.z/2);
+            down(conn_size.z/4) cube([conn_size.x, conn_size.y, conn_size.z/2], center=true);
+        }
+    }
+    down(pin_size.z)
+    translate(get_platform_lock_pin_pos()) {
+        fwd(pin_size.y) scale([1, -1, -1]) lock_pin();
+        socket_connector();
+    }
+}
+module platform_locks_pins() {
+    platform_size=get_platform_size();
+    lock_pin_size=get_platform_lock_pin_size();
+    module lock_side(groove) {
+        translate(get_platform_lock_pin_pos()) lock_mechanism();
+    }
+    lock_side();
+    scale([1, -1, 1]) lock_side();
+}
+module platform_locks_sockets() {
+    lock_socket();
+    scale([1, -1, 1]) lock_socket();
+}
 module platform(base) {
     size=get_platform_size();
+    base_size=size;
+    wall=get_platform_wall();
+    top_size=get_platform_top_size();
     top=!base;
-    up(top?size.z:0)
-    color(top?"Olive":"YellowGreen")
-    cube(size, center=true);
     
+    module base_platform() {
+        module base_platform_core() {
+            braced_thinning_wall(h=size.y, l=size.x, thick=size.z, wall=0, strut=wall, orient=ORIENT_X_90);
+        }
+        
+        difference() {
+            base_platform_core();
+            translate(get_platform_top_pos()) down(top_size.z/2) prismoid(size1=[top_size.x,top_size.y], size2=[base_size.x-2,base_size.y-2], h=top_size.z);
+            lock_buttons_cutout();
+        }
+    }
+    module top_platform() {
+        up((base_size.z-top_size.z)/2)
+        braced_thinning_wall(h=top_size.y, l=top_size.x, thick=top_size.z, wall=0, strut=wall/4, orient=ORIENT_X_90);
+    }
+        
     module strap_connectors() {
-        down(size.z/2) foreach_platform_strap_connector() {
+        //down(size.z/2)
+        foreach_platform_strap_connector() {
             link_connector_pin();
         }
     }
     
+    color(top?"Olive":"YellowGreen")
     if (base) {
+        base_platform();
+        platform_locks_pins();
         strap_connectors();
+    } else {
+        top_platform();
+        platform_locks_sockets();
     }
 }
 
@@ -61,6 +152,12 @@ module model_platform_strap() {
 }
 
 // Export:
-if (is_model(MODEL_PLATFORM_HARNESS)) model_platform_harness();
-if (is_model(MODEL_PLATFORM_STRAP)) model_platform_strap();
-if (is_model(MODEL_DEMO)) model_prop_arm();
+difference() {
+    union() {
+        if (is_model(MODEL_PLATFORM_HARNESS)) model_platform_harness();
+        if (is_model(MODEL_PLATFORM_STRAP)) model_platform_strap();
+        //if (is_model(MODEL_DEMO)) model_prop_arm();
+    }
+    // xray:
+    //left(500+5) cube([1000, 1000, 1000], center=true);
+}
\ No newline at end of file
diff --git a/src/specs_platform.scad b/src/specs_platform.scad
index 51b9b15..ea734de 100644
--- a/src/specs_platform.scad
+++ b/src/specs_platform.scad
@@ -2,13 +2,22 @@ use <specs_phone.scad>
 use <specs_strap.scad>
 
 function get_platform_size() = [
-    get_phone_size().x - 5,
+    get_phone_size().x - 30,
     get_phone_size().y - 5,
-    5
+    get_platform_wall()*3
+    ];
+function get_platform_top_size() = [
+    get_platform_size().x - 2*get_platform_wall(),
+    get_platform_size().y - 2*get_platform_wall(),
+    get_platform_size().z - get_platform_wall()];
+function get_platform_top_pos() = [0, 0, (get_platform_size().z-get_platform_top_size().z)/2];
+function get_platform_wall() = 3;
+function get_platform_strap_connector_offset() = [
+    (get_platform_size().x/2 - get_link_segment_size().y/2) - 3,
+    get_platform_size().y/2 + 4,
+    -get_link_segment_size().z/2 + 0.5
     ];
 
-function get_platform_strap_connector_offset() = [
-    (get_platform_size().x/2 - get_link_segment_size().y/2),
-    get_platform_size().y/2,
-    -get_link_segment_size().z/2
-    ];
+function get_platform_lock_pin_size() = [20, 4, 3];
+function get_platform_lock_arm_size() = [65, 2, 3];
+function get_platform_lock_pin_pos() = [-20, -get_platform_top_size().y/2 + get_platform_wall()*4 + 1, get_platform_top_size().z/2];