Lc1 = 0.1;

Point(3) = {  0.1,  1.0, 0.0, Lc1};
Point(4) = {  0.1,  0.0, 0.0, Lc1};
Point(5) = {  0.5,  1.0, 0.0, Lc1};
Point(6) = {  0.5,  0.0, 0.0, Lc1};
Line(1)  = {3, 4};
Line(2)  = {4, 6};
Line(3)  = {6, 5};
Line(4)  = {5, 3};

Line Loop(17) = {1, 2, 3, 4};
Plane Surface(50) = {17};

Physical Line (100) = {1};
Physical Line (101) = {3};

Physical Surface (120) = {50};