If you want a 45° chamfer using the native tools, offset from the inside edges of the box. Then move the interior edges down by the same amount. No need for a guide line that just needs to be deleted later.

One possibility is that if you are "looking through" the hole as you push-pull, the tool naturally stops at the opposite face because there is no other inference in that direction based on the cursor's location. This doesn't happen when you are viewing more from the side so that the tool can find a meaningful distance to extrude based on the cursor position. [image: mDp5_pushpull.gif]

never mind got it figured out... thanks again