for (y = [-1, 1]) scale ([1, y, 1])
translate([sponge_h/2+wall, sponge_w/2+wall/2, (sponge_l+wall)/2])
rotate([90, 0, 0])
perf_wall(w = sponge_h + 2*wall, h = sponge_l + wall, d = wall,
for (y = [-1, 1]) scale ([1, y, 1])
translate([sponge_h/2+wall, sponge_w/2+wall/2, (sponge_l+wall)/2])
rotate([90, 0, 0])
perf_wall(w = sponge_h + 2*wall, h = sponge_l + wall, d = wall,