The base is about three by three inches. The beam is about one and one half by three inches. I have 1/4 inch all thread as the clamp with t-nuts mounted in "handles" to tighten. I use painters tape along the edge of the staple board on the top, glue it up, alight every thing and place it in the clamp then tighten it down...... I have a block inside the sound box to support the top to the staple board.