bare-high/gpt-5.4 / tier-2-l-bracket

```openscad
$fn = 64;

width = 50;
depth = 40;
height = 40;
thickness = 3;

through_d = 4.5;
csk_d = 8;
csk_depth = 2;

edge_offset = 10;
eps = 0.1;

hole_x = width / 2 - edge_offset;

module l_bracket() {
    union() {
        // Horizontal flange
        translate([-width / 2, 0, -thickness])
            cube([width, depth, thickness]);

        // Vertical flange
        translate([-width / 2, -thickness, 0])
            cube([width, thickness, height]);

        // Corner material for a connected sharp bend
        translate([-width / 2, -thickness, -thickness])
            cube([width, thickness, thickness]);
    }
}

module countersunk_hole_horizontal(x, y) {
    // Through hole
    translate([x, y, -thickness - eps])
        cylinder(h = thickness + 2 * eps, d = through_d);

    // Countersink on outer side (bottom)
    translate([x, y, -thickness - eps])
        cylinder(h = csk_depth + eps, d1 = csk_d, d2 = through_d);
}

module countersunk_hole_vertical(x, z) {
    // Through hole
    translate([x, -thickness - eps, z])
        rotate([-90, 0, 0])
            cylinder(h = thickness + 2 * eps, d = through_d);

    // Countersink on outer side
    translate([x, -thickness - eps, z])
        rotate([-90, 0, 0])
            cylinder(h = csk_depth + eps, d1 = csk_d, d2 = through_d);
}

difference() {
    l_bracket();

    for (x = [-hole_x, hole_x]) {
        countersunk_hole_horizontal(x, depth / 2);
        countersunk_hole_vertical(x, height / 2);
    }
}
```