How to Build a Bench Seat Over a Heat Duct

Arrange two 1 1/2 by 3 1/2 by 16-inch boards parallel to each other on the working surface with their largest surfaces down. Position two additional boards of the same dimensions on top of them but perpendicular to the original boards. Adjust the spacing of the boards so that they overlap on the corners only, with all edges being even in a perfect 16-inch square.

Drill two holes down through both boards at each corner, for a total of eight holes. Set 2 1/2-inch wood screws in each hole and secure the boards together tightly. Repeat with four additional boards to make the two leg systems of the bench.

Prop the two leg systems up so that they are vertical, using the help of an assistant. Set four 1 1/2 by 3 1/2 by 36-inch boards on top of these leg systems to serve as the seat boards and spread them out so that they are evenly spaced on top of the leg systems. Adjust the spacing of the leg systems underneath the seat boards so that the leg systems are even but also avoid the heat duct.

Attach each seat board to both leg systems by making two holes down through the seat board and into each leg system for a total of 16 holes. Set 2 1/2-inch wood screws in each hole and tighten them down completely to secure the pieces together.