wall_h = 30;
wall_t = 5;
t = 5;

doniczka_d = 105;
wall_w = doniczka_d+2*t;
dystans=20;

union() {
  // wall mount
  translate([-wall_t, -wall_w/2]) cube([wall_t, wall_w, wall_h]);
  difference() {
    union() {
      translate([0,-wall_w/2,0]) cube([wall_w/2+dystans, wall_w, t]);
      translate([wall_w/2 + dystans,0, 0])
        cylinder(d=wall_w, h=t, $fn=100);
    }
    translate([wall_w/2 + dystans,0,-0.1]) cylinder(d=doniczka_d, h=t+0.2);
  }
}