diff --git a/shelf_with_drawers.scad b/shelf_with_drawers.scad
index 4cb1944..36f4a8c 100644
--- a/shelf_with_drawers.scad
+++ b/shelf_with_drawers.scad
@@ -45,11 +45,11 @@ module drawer()
     {
         translate([board_height, 0, 0])
         {
-            cube([drawer_size - board_height * 2, board_height, drawer_size]);
+            cube([drawer_size - (board_height * 2), board_height, drawer_size]);
         }
         translate([board_height, drawer_size - board_height, 0])
         {
-            cube([drawer_size - board_height * 2, board_height, drawer_size]);
+            cube([drawer_size - (board_height * 2), board_height, drawer_size]);
         }
     }
 
@@ -59,7 +59,8 @@ module drawer()
         translate([board_height, board_height, 0])
         {
             cube([
-                drawer_size - board_height * 2, drawer_size - board_height * 2,
+                drawer_size - (board_height * 2),
+                drawer_size - (board_height * 2),
                 board_height
             ]);
         }
@@ -98,7 +99,7 @@ module shelf()
             {
                 translate([x, y, 0])
                 {
-                    lath(80 + 4 * drawer_size + 5 * board_height);
+                    lath(80 + (drawer_size * 4) + (board_height * 5));
                 }
             }
         }
@@ -127,9 +128,9 @@ module shelf()
     {
         for (z = [
                  80, 80 + drawer_size + board_height,
-                 80 + drawer_size * 2 + board_height * 2,
-                 80 + drawer_size * 3 + board_height * 3,
-                 80 + drawer_size * 4 + board_height * 4
+                 80 + (drawer_size * 2) + (board_height * 2),
+                 80 + (drawer_size * 3) + (board_height * 3),
+                 80 + (drawer_size * 4) + (board_height * 4)
              ])
             translate([lath_width, 0, z])
             {
@@ -147,11 +148,11 @@ translate([lath_width, -10, 80 + board_height])
     {
         drawer();
     }
-    translate([0, 0, drawer_size * 2 + board_height * 2])
+    translate([0, 0, (drawer_size * 2) + (board_height * 2)])
     {
         drawer();
     }
-    translate([0, 0, drawer_size * 3 + board_height * 3])
+    translate([0, 0, (drawer_size * 3) + (board_height * 3)])
     {
         drawer();
     }