Why does this Boolean Diiference fail with surface beyond object

[Steve1]

Hi,
V5

First failure coplanar at top, then at base then solve those then still it fails, but why ?
why boolean difference fail.3dm (234.0 KB)

I love Booleans.

Steve

[tay.othman (tay.0)]

It’s likely because of rhino having hard time to figure out the splitting at these corners. Have you tried using Trim by curve?

[pascal (Pascal Golay)]

Hello, this works fine in V7, if you are working in an earlier version where it fails for some reason, use Intersect, Split and/or Trim.

-Pascal