The aft end of the sliding seat rowing rig for the Wherry requires drilling a hole through the metal I frame of the rig, and then through the seat, in order to bolt the rig to the boat.  This is complicated by the fact that there is an additional metal bracket right at the key spot on the metal frame (as can be seen in the picture below, if I post it sucessfully)

While trying to figure out how to do this without compromising the strength of the components, I noticed that there are factory embedded thredded nuts along the undersurface of the rig down at the aft end.

So, I realized that one could just drill through the seat (and reinforcement block in just the spot), and thread some bolts up from below into these pre-existing thredded bolts, rather than having to drill through the rig and compromise its integrity.  Also, this way you get two bolts instead of just one.

You still have to do the drill thru the metal routine for the front seat bolt, but that has lots of leeway.

Hope this helps someone who's workong on this next.

Hickory