Like R.D. said, 1/2" rebar, 10' long is a good length for most situations. 3/8" with much use turns into a straightened pretzel, and will bend easier every time. Also, you need the backbone of 1/2" to get the rod into the bottom in hard bottom situations. Rebar works just as good as cold steel and is cheaper. I weld a stop up 18" from the end. Washers welded on the top end are fine, but you will have to have your lock on permanently if you do this. I do it this way, and just use mighty hooks for attaching the trap to the lock when needed. In the picture, the bend in the rod is there only because of the weight of the trap. A small bend is helpful though to make sure the rod is clear of the bottom and the lock can slide smoothly to the bottom.