It's basically a large piece of cardboard with movable burning holes of various sizes and shapes. You can put any shape in any hole, making customization quick and easy. And because the cutouts are round, you can orient them at any angle. I also included flaps over each location so I could block out the ones I wasn't using. The picture below shows part of the tool with one of the flaps up to reveal an insert with a square hole.

The tool is constructed on two layers. The bottom piece is 14" by 16" mat board, black on one side and white on the other. The black side goes toward the print, which cuts down on reflected light. I found out the hard way that using white on both sides would cause fogging.

Using an X-ACTO knife, I cut nine evenly spaced holes of about 31/4" diameter. You might want to mark out a grid with pencil (to mark the centers of the circles) and then draw the circles with a compass.

The upper layer is thicker stuff, commonly called presentation board or foam core board. Its about 3/16" and at least one side needs to be white. I cut 4" holes in it to match the nine in the mat board. Be sure that the circles are concentric, since you want a nice even "ledge" on which to rest the burning tools.

Once you've got the holes cut, glue the two pieces together with some white glue, like Elmers. Use some between all the holes. If the two pieces can separate, it invites light leaks.

The burning tools are circular pieces cut from the same black/white mat board. They should be just smaller than the holes in the presentation board. You'll need at least nine of them…one for each hole. I went ahead and made some extra round blanks in case I wanted to make some custom tools later. The picture below shows how the tools sit in the insets.

The cover flaps are 4 ¾' squares made from the same black/white mat board. Tape them into place with light colored masking tape.

When I'm using the thing, I turn on the enlarger with the flap open and my hand under the hole. Once I get the tool positioned I remove my hand and start the burn.

This is a very flexible tool! You can use any shape in any location, and because they are round, you can rotate them to any desired angle. The white top makes it easy to see what you're burning, and the black bottom holds down fog.

I've found that it makes burning a much easier task.