This rod will align the scope horizontally, but I have seen a lot of base and ring combinations there were out of alignment vertically, for varirous reasons, the primary one being military rifles that had the receiver rings ground down to clean them up, and because of manufacturing tolerences between batches of bases.
In many instances, either the front or rear base would need to be shimmed, because to put the scope in the rings with the bottom of either ring lower than the other would cause warpage of the scope tube.
To test for this, I would position both rings, leaving the top off both. Then, I would install the scope, just using one entire ring, most times the front one. If there was a small space between the scope tube and the bottom inside of the rear ring, then that base would need shimming.
This would not tell you whether or not the front base or ring was lower, however, so I would reverse the procedure, tightening the rear ring but leaving the front cap loose. If gap present, then this would mean the front base would need shimming.
For proper, stress free mounting and alignment, the scope tube needs to in alignment both vertically and horizontally.
Lapping would not cure this. You could get a good fit of sorts, but in the above situation, where either the front ring or base was not of the same height, lapping would make the hole in one or the other rings egg shape.
Meaning, you would lap away the high part of the inside bottom of the ring to make an even fit in both rings, and if it was the receiver or base, or even the ring height that was off, you would be lapping off material in the ring to correct another misaligned part.
This is where a 2 piece, sharp pointed rod would be helpful. You could align the sharp points both vertically and horizontally.
