Auto Parts: Installing a trailer hitch, trailer hitches, rv dealer

Question
Hello,

I'm installing a trailer hitch that I removed from another vehicle.  Some of the bolts fit into pre-threaded areas of the body of the car.  But in two places, either the bolt or the nut must be fished to a position where a hole is, but not threaded.  What technique or type of tool do I use to position and stabilize the bolt or nut, to tighten and make the connection?

Thanks

Answer
    If you go to a store that specializes in hitches (like an RV dealer), they can sell you the solution.  It is a nut with a long thin wire spot-welded to it that can be fished into the frame and used to secure the bolt.  Get them to show you the other neat tricks that they have, some of the others may be useful, too.  When we started installing trailer hitches at our shop, I was amazed at how clever the hitch manufacturers were at thinking up different ways to do things.