Hi bb, so you have probably already seen that you can cut a hole all the way through an object by drawing a circle and using it as the cutting object in a boolean?

Like Paolo mentions if you don't want the cut to go all the way through then like Paolo says above you need to create a cylinder of the depth you want and then use that cylinder as the cutting object.

You can use either the Draw solid > Cylinder command for that, or a more general purpose way is to use Extrude on your cutting curves to punch them out into a solid, then use the extruded shape as the cutting object.

So for example if you have this tube and a circle for the hole you wish to create like this:



If you use the circle as the cutting object in the boolean, it will go all the way through like this:




But if you select your circle and use Extrude to punch it out into a solid that does not go all the way through the other object, like so:



Then you can use that extruded piece as the cutting object to make your hole only on one side and not the other:



- Michael