! Document name: inv_frame

!name: inv frame  28.04.1989.

let c=2 1/2"
poly_ 10,
0,0,1,
a,0,1,
a,b,1,
0,b,1,
0,0,0,
c,c,0,
c,b-c,0,
a-c,b-c,0,
a-c,c,0,
c,c,0
end