$fn=64;

// --- Parameters ---
rail_length = 500;
rail_base_width = 30;     // Width against the wall
rail_top_width = 40;      // Width at the front (creates a printable dovetail)
rail_thickness = 10;      // Depth of the rail
hole_spacing = 100;       // Distance between mounting holes
hole_diameter = 4.5;      // Clearance for M4 or #8 screws
countersink_diameter = 9; // Diameter of screw head
countersink_depth = 3;    // Depth of the angled screw head

// --- Main Model ---
module wall_rail() {
    difference() {
        // Main rail profile (dovetail/chamfered shape)
        translate([0, -rail_length/2, 0])
            rotate([-90, 0, 0])
            linear_extrude(height=rail_length)
            polygon([
                [-rail_base_width/2, 0],
                [rail_base_width/2, 0],
                [rail_top_width/2, rail_thickness],
                [-rail_top_width/2, rail_thickness]
            ]);

        // Mounting holes
        num_holes = floor(rail_length / hole_spacing);
        start_y = -(num_holes - 1) * hole_spacing / 2;

        for (i = [0 : num_holes - 1]) {
            translate([0, start_y + i * hole_spacing, 0]) {
                // Screw shaft clearance
                translate([0, 0, -1])
                    cylinder(h=rail_thickness + 2, d=hole_diameter);

                // Countersink angled cone
                translate([0, 0, rail_thickness - countersink_depth])
                    cylinder(h=countersink_depth + 0.01, d1=hole_diameter, d2=countersink_diameter);

                // Countersink top clearance (ensures manifold subtraction)
                translate([0, 0, rail_thickness])
                    cylinder(h=2, d=countersink_diameter);
            }
        }
    }
}

// Render the object
wall_rail();