$fn = 64;

// --- Parameters ---
rail_length = 300;
rail_width = 30;
rail_thickness = 12;
dovetail_inset = 5;

num_holes = 5;
hole_margin = 25;
hole_diameter = 4.5;       // Clearance for M4 screws
head_diameter = 9.0;       // M4 screw head diameter
countersink_depth = 3.0;

// --- Main Model ---
difference() {
    // Rail Body (Dovetail Profile)
    hull() {
        // Base touching the wall
        translate([-rail_length/2, -rail_width/2, 0])
            cube([rail_length, rail_width, 0.01]);
        
        // Top face of the rail
        translate([-rail_length/2, -rail_width/2 + dovetail_inset, rail_thickness - 0.01])
            cube([rail_length, rail_width - 2*dovetail_inset, 0.01]);
    }
    
    // Mounting Holes
    for (i = [0 : num_holes - 1]) {
        x_pos = -rail_length/2 + hole_margin + i * ((rail_length - 2*hole_margin) / (num_holes - 1));
        
        translate([x_pos, 0, 0]) {
            // Main screw shaft
            translate([0, 0, -1])
                cylinder(h = rail_thickness + 2, d = hole_diameter);
            
            // Countersink for flathead screws
            translate([0, 0, rail_thickness - countersink_depth])
                cylinder(h = countersink_depth + 0.02, d1 = hole_diameter, d2 = head_diameter);
                
            // Counterbore clearance (extends slightly above to ensure clean cut)
            translate([0, 0, rail_thickness])
                cylinder(h = 1, d = head_diameter);
        }
    }
}