I have 4x8 sheets on my barn walls in a few areas to hold tools. Most of my tools with handles have holes drilled through them so the can hang on nails. I use 12D or 16D nails, clip off the heads, and drive them into 1/8" pre-drilled holes. They hold well even for the heavier stuff like sledge hammers or mattocks. I use plywood because it seems to hold the nails better.