Altering particleboard shelf -tips?

You mean to use as a template?
… That is brilliant…
What would you suggest? Just c-clamp a strip of peg board to the shelf board, and drill away?

Any pointers on how to avoid drilling too deep and going through the boards? What about keeping the holes straight? I think a drill press could do that, but would that be over the top? Would a handheld drill just cause too many headaches?

Also, any idea if the holes of the peg board would be a snug fit for shelf pegs? Seems like the best way for this idea to work would be to use a bit the size of the holes so there’s no wobbling around while trying to center the bit in each hole…