Clopper, so far it's all NURBS, so all the holes or rounded edges you see are either trimmed surfaces or fillets. Here's another pic that demonstrates the use of NURBS a little better.

An example is the hexagonal bolts which are really easy with NURBS. Just make a NURBS circle with 12 spans, then select every other CV around the surface and rotate them until you have a hexagonal shape with nice rounded corners. Then duplicate it, move the duplicate, and loft between the two. Finally, create a NURBS plane and intersect it with the lofted surface (this will be the bolt top), and then do a circular fillet between the lofted surface and the plane (make sure "create curve on surface" is checked so you can trim off the unneeded edges). Voila you have a nice looking nut, with rounded edges, all in about 30 seconds.

I'm no pro, just a hobbyist for now.