msize=0.8;
//LITTLE BOX
Point(0)={1,1,-2,msize};
Point(1)={-1,1,-2,msize};
Point(2)={-1,-1,-2,msize};
Point(3)={1,-1,-2,msize};

Line(4)={0,1};
Line(5)={1,2};
Line(6)={2,3};
Line(7)={3,0};

Line Loop(8) = {4,5,6,7};
Plane Surface(9) = {8};
littlebox [] = Extrude{0,0,4}{Surface{9};};

//BIG BOX
Point(100)={2,2,-4,msize};
Point(101)={-2,2,-4,msize};
Point(102)={-2,-2,-4,msize};
Point(103)={2,-2,-4,msize};

Line(104)={100,101};
Line(105)={101,102};
Line(106)={102,103};
Line(107)={103,100};

Line Loop(108) = {104,105,106,107};
Plane Surface(109) = {108};
bigbox [] = Extrude{0,0,8}{Surface{109};};

// Volume(3)={1,2};