Point(0) = {0, 0, 0, 0.1};
Point(1) = {1, 0, 0, 0.1};
Point(2) = {1, 1, 0, 0.1};
Point(3) = {0, 1, 0, 0.1};
Line(1) = {0, 1};
Line(2) = {1, 2};
Line(3) = {2, 3};
Line(4) = {3, 0};
Line Loop(6) = {3, 4, 1, 2};
Plane Surface(6) = {6};
Extrude {0, 0, 1} {
  Surface{6};
}