[Stiglr]

"Make Hole" uses the shape of the surface itself to base the hole on, and you set the % of the area that makes up the hole.

If you want a different shaped hole in a particular object or surface, you may have to rely on a Boolean operation to do this. It's "messy" and might not be worth it for you, but basically...

1) Create a poly in the shape of the hole you want,
2) Extrude the poly
3) Position the new "cutout" poly such that it intersects the item you wish to create the hole in, and assign both two-sided surfaces.
4) Do a Boolean subtraction, B-A, using the "hole-shaped item" as A and the item you wish to create the hole in as B; set the Boolean subraction to NOT save the original items. (Remember, if it doesn't work the way you want, you can Undo the operation [or change the operands] until you do get it right).

After you perform the Boolean, you may have to do a LOT of cleanup of inadvertent leftover polys, and stuff on the "inside" of the object. Booleans can also cause the creation of new polys and triangles around the edges of a hole that are, to put it mildly, inefficient. For these reasons alone, it might be better for you to use "Add vertice" operations on the surface to manually "outline" the area you wish to cut out of an object, then delete the area. You might even use an intersecting object (as outlined above, stopping short of doing the boolean) as a temporary guide to help you accurately place the new vertices for a manual cut.