diff --git a/README.md b/README.md
index c38732d..66a11e4 100644
--- a/README.md
+++ b/README.md
@@ -42,14 +42,34 @@ This model is parameterised and is resizeable within limits, but if you vary any
 
 Colours are for clarity only.
 
+## Parameters
+
+height=950, width=1500, nplanks=4, ndowels=4, plank_width=150, plank_gap=20, top_thickness=75, leg_section=100
+
+The following parameters may be passed to the `bench` module:
+
+| Parameter     | Default | Documentation                                             | Sensible range |
+| ------------- | ------- | --------------------------------------------------------- | -------------- |
+| height        | 950     | height of bench top                                       | 800-1100       |
+| width         | 1500    | overall width of the bench, excluding the end vice winder | 1200-2000      |
+| nplanks       | 4       | number of planks comprising the top                       | 2-5            |
+| ndowels       | 4       | number of dowels joining each adjacent plank pair         | 2-8            |
+| plank_width   | 150     | width of each plank                                       | 150-300        |
+| plank_gap     | 20      | gap between each pair of planks                           | 0-20           |
+| top_thickness | 75      | thickness of the planks comprising the top                | 60-100         |
+| leg_section   | 100     | thickness of the (square section) legs                    | 75-150         |
+
+
+
 ## Errata/todo:
 1. locking wedges and treenails are generally not present in this 
      drawing;
 2. mortices and holes for wedges and treenails are not all present;
 3. two of the tapered mortices for the longitudinal braces are the 
      wrong way round;
-5. while all tenons are modelled, not all mortices are; where a tenon
+4. while all tenons are modelled, not all mortices are; where a tenon
      intersects an apparently solid piece, assume there is a mortice!
+5. screw threads are not yet modelled.
 
 ## Licence
 
diff --git a/roubo.scad b/roubo.scad
index ebcb4c7..f54dd72 100644
--- a/roubo.scad
+++ b/roubo.scad
@@ -171,15 +171,19 @@ module top_plank(bench_width = 1500, plank_width= 150, top_thickness=75) {
     };    
 }
 
-//top_plank();
-
-module top_end(depth=600, section=75) {
+module top_end(nplanks=4, plank_gap=20, plank_width=150, section=75) {
+    depth = (nplanks*plank_width) + (plank_gap * (nplanks - 1));
+    
     color("green")
-        cube([ depth, section, section]);
-    // todo: add mortices
+        difference() {
+            cube([ depth, section, section]);
+            for ( plank = [1:nplanks]) {
+                translate([(plank -1) * (plank_width + plank_gap), 0, 0]) 
+                    top_plank_end_tenon( plank_width, section);
+            };
+        };
 }
 
-
 module end_vice_cut( plank_width=150, width=300, top_thickness=75) {
     translate([plank_width * 0.375, 0, -1])
     cube([plank_width/4, width, top_thickness + 2]);
@@ -211,6 +215,10 @@ module vice_screw(depth=400) {
             }
 }
 
+/**
+ * todo: the block doesn't get correctly centred in the slot if the
+ * plank_width isn't 150mm, so I've got geometry wrong.
+ */
 module end_vice( plank_width=150, width=300, top_thickness=75){
     // the end vice block: this has exactly the section of the end 
     // vice cut, so we'll use the same model (but much smaller width)
@@ -218,8 +226,8 @@ module end_vice( plank_width=150, width=300, top_thickness=75){
         translate([50 - (width/5), 0, 0])
             end_vice_cut( plank_width, 50, top_thickness); 
     rotate([0, 0, 90])
-    translate([width *1.1, 0 - plank_width/2, top_thickness/2])
-    vice_screw(width);
+        translate([width *1.1, 0 - plank_width/2, top_thickness/2])
+            vice_screw(width);
 }
 
 module bench_top( nplanks=4, ndowels = 4, plank_gap=20, bench_width=1500, plank_width=150, top_thickness=75) {
@@ -244,10 +252,13 @@ module bench_top( nplanks=4, ndowels = 4, plank_gap=20, bench_width=1500, plank_
             }
         }
     }
+    //module top_end(nplanks=4, plank_gap=20, plank_width=150, section=75) {
+
     translate([0, 1, 0])
-        top_end((plank_width * nplanks)+(plank_gap * (nplanks - 1)), top_thickness);
-    translate([ 0, bench_width - (top_thickness +1), 0])
-        top_end((plank_width * nplanks)+(plank_gap * (nplanks - 1)), top_thickness);
+        top_end( nplanks, plank_gap, plank_width, top_thickness);
+    translate([ 0, bench_width - 1, top_thickness])
+        rotate([ 180, 0, 0])
+            top_end( nplanks, plank_gap, plank_width, top_thickness);
 
 } 
 
@@ -305,14 +316,14 @@ module front_vice( width=150, height=800, depth=400) {
     color("fuchsia")
         translate([0-(depth*0.8), (width/2)-(width/12), width/2])
             difference() {
-                cube([depth, width/6, width/2]);
+                cube([depth, width/6, 75]);
                 for( hole_pair=[1:5]) {
-                    translate([25+(depth/10 * hole_pair), width/3, width/6])
-                    rotate([90,0,0])
-                        cylinder(width/2, r=12.5);
-                    translate([(depth/10 * hole_pair), width/3, width/3])
-                    rotate([90,0,0])
-                        cylinder(width/2, r=12.5);
+                    translate([25+(depth/10 * hole_pair), 50, 25])
+                        rotate([90,0,0])
+                            cylinder(width/2, r=12.5);
+                    translate([(depth/10 * hole_pair), 50, 50])
+                        rotate([90,0,0])
+                            cylinder(width/2, r=12.5);
                 }
             };
     translate([(depth*0.22), width/2, height * 0.75])
@@ -334,4 +345,8 @@ module bench( height=950, width=1500, nplanks=4, ndowels=4, plank_width=150, pla
 //translate([0, 0, 875])
 //    bench_top();
 
-bench(width=1700);
\ No newline at end of file
+bench();
+translate([1000, 0, 0])
+    bench(width=1700, nplanks=3, plank_width = 200);
+
+//legs();
\ No newline at end of file