Modern A-Frame Bookshelf

Cut the four legs with both ends at 10° off square, parallel to each other, so the shelf sits level while the legs lean. A miter saw makes matching cuts easiest, but a protractor with a jigsaw or circular saw works — the key is that all four legs are identical, or the frame will twist.

The supports are all 2x4 cut to match your shelf width — measure your shelving first. If you bought nominal 12" (really 11-1/4"), cut the supports at 11-1/4"; for full 12" material, cut 12". Mark and attach the supports to the legs at each shelf level.

Mark each shelf from the ends so the marks line up with the shelf supports, then screw the shelves down to the supports with 2" screws and glue. Screw the leg-to-support joints with 3" screws. Sand and finish. Keep books to the middle of the longer spans if you're near the 36" limit.