Spacer Jig for Deck Beam

I'm building a deck supported by drop-beams, which I'm making out of 2x10 lumber separated by plywood spacers. This jig fits on the top edge (i.e., the side) of a 2x10 and helps you position your spacer.

It has a viewing hole with two arrows to locate marks on the side of the board.

The 90° angle receives the spacer, which I'm assuming you made with a point facing upward to help it shed water. The exact shape or size of the spacer isn't critical.

The back side has a cutout, in case you're making a multi-layer beam. My beam has 3 layers. This helps position the spacer in front of the previous layer's spacer, so your nails will go solidly through all the layers.