How can I create a hole in a solid that has one surface at 45 degrees. The other is horizontal.
Shep has given you a good answer for your specific case.
Stepping back a pace, you can make a hole of any cross-section into or through an object of any shape using the Intersect command. Just make an extrusion of arbitrary length (a positive shape, like a rod) representing the hole and position it so that it passes through the object where you want the hole. It can enter the object at whatever angle and location you wish. If it’s a blind hole, just position the extrusion so that it ends inside the object.
Select just the wall of the extrusion and use Intersect with Model. Select both the extrusion and the object and use Intersect with Selected. Then just remove excess material, leaving the original object with the specified hole in it. The wall of the extrusion becomes the wall of the hole.
This is a video going over gully’s reference to intersect command
Thanks! That is exactly what I wanted.
Thanks for you help. This has been very instructive.