I can't find it anywhere, more of an accessory that a tool.
Essentially it's used for pushing into angle so that the plastic pins/sticks move down and leave an in print in the tool.
It's about 30cm x 20 cm and made of plastic, the one I used was blue. The sticks/pins were really close together and held together by some king of brace/belt.
here is a bad word picture of the tool on the left and then when you push it into an angle the pins move down leaving the shape of the angle in the tool.