I built some trolling rod holders this weekend. I used 1x1x1/8 inch angle iron, a 1/2x12inch steel nipple (not galvanized!!!!), a 1/2 inch threaded floor plate.
I cut the angle 18 inches and drilled 11/32 holes about 2 1/2 inches from each end. I then welded one end of the nipple to the center of the angle. I purchased some no-name rod holders from th Grizzly Jig Co. which were metric threaded so they wont fit Driftmaster of Attwood holders. I tapped the 11/32 holes with a 10mm tap and the rod holders screwed right in. They lock down with a wing nut. I painted them with flat black Rustoleum and put the floor plates on the bottom of the nipples. You can put several floor plates in your boat to move the holders around. If your interested in pics, leave me a pm with your e-mail and I'll try to send them since the pics are toob big to post here.
I'd be happy to build some sets for someone interested in putting me on some slabs at either Sardis or Enid MS anytime the week of April 15 through the 22