$fn=64;

// --- Parameters ---
rail_width = 20.5;     // Inner width (slightly oversized for clearance)
rail_height = 20.5;    // Inner height
wall_thickness = 3.0;  // Wall thickness of the connector
insertion_depth = 35;  // How far the rail inserts into each side
screw_hole_dia = 4.0;  // Diameter of the securing screw holes

// --- Derived Dimensions ---
outer_w = rail_width + (wall_thickness * 2);
outer_h = rail_height + (wall_thickness * 2);
arm_length = outer_w + insertion_depth;

// --- Main Geometry ---
difference() {
    // Outer Shell (L-Shape)
    union() {
        // X-Axis Arm
        cube([arm_length, outer_w, outer_h]);
        // Y-Axis Arm
        cube([outer_w, arm_length, outer_h]);
    }

    // Inner Hollow Cutouts for Rails
    union() {
        // X-Axis Cutout
        translate([wall_thickness, wall_thickness, wall_thickness])
            cube([arm_length, rail_width, rail_height]);
        // Y-Axis Cutout
        translate([wall_thickness, wall_thickness, wall_thickness])
            cube([rail_width, arm_length, rail_height]);
    }

    // Securing Screw Holes
    // X-Arm Top/Bottom Hole
    translate([outer_w + (insertion_depth / 2), outer_w / 2, -1])
        cylinder(d=screw_hole_dia, h=outer_h + 2);
        
    // X-Arm Side Hole
    translate([outer_w + (insertion_depth / 2), -1, outer_h / 2])
        rotate([-90, 0, 0])
        cylinder(d=screw_hole_dia, h=outer_w + 2);

    // Y-Arm Top/Bottom Hole
    translate([outer_w / 2, outer_w + (insertion_depth / 2), -1])
        cylinder(d=screw_hole_dia, h=outer_h + 2);
        
    // Y-Arm Side Hole
    translate([-1, outer_w + (insertion_depth / 2), outer_h / 2])
        rotate([0, 90, 0])
        cylinder(d=screw_hole_dia, h=outer_w + 2);
}