!1/2_grid_2  /rewritten 2/16/94/***VL/
!a,b,frame width,frame thickness/6=grid thickness

e=c/2
g=1.5*c
z=a/2-g
f=b-g
r=a/2/b
x=sqr((e/2)**2+(e/2*r)**2)
k=r*g+x
l=r*g-x
m=(z-0.006)*sin(45)          !***-0.006: arc approx. error correction
n=(f-0.006)*sin(45)           !***-0.006: arc approx. error correction
y=x/2/r
gosub 10
mulx -1
gosub 10
del 1
prism_ 4,d,
-e/2,g,15,
e/2,g,15,
e/2,f-0.004,15,                  !***-0.004: arc approx. error correction
-e/2,f-0.004,15                 !***-0.004: arc approx. error correction
end
10:
prism_ 4,d,
l,g,15,
k,g,15,
m+x/2,n-y,15,
m-x/2,n+y,15

return
