Three-Month Rotating Wall Calendar Shelf

On one of the 1x6 boards, mark the side edges at 1-5/8", 17-1/8", and 32-3/8" from one end — these are your divider centerlines. On all three 1x3 dividers, mark 4-3/4" inward from both cut ends along the edge.

Place the three 1x3 dividers on edge on a flat, level surface. Lay the marked 1x6 on top at your layout lines and screw down, two screws per shelf joint. Check each divider is perpendicular to the shelf board with a speed square as you go — this is what keeps the slots even.

Place the remaining 1x6 boards on the back of the assembly and mark screw locations at each divider joint. Screw the back boards on with two screws per joint.

Sand any rough edges, apply paint or stain if you're finishing it, then hang on the wall with the picture-hanging bracket — level it before you commit to the final screw holes. Slide the three calendar panels into their slots.