Abstract: A device for punching two parallel narrow slots in a sheet of paper at 45 degrees to one edge of the sheet and spaced apart slightly less than the corner-to-corner diagonal dimension of a card which is to be attached to that sheet by inserting diagonal corner segments into the slots. The slot-punching device has a generally flat base with an adjustable stop. A lever arm pivoted on the base carries two punches with respective narrow blades for reception in the base when the lever arm is lowered. A reciprocable head on top of the lever arm is depressed to push the punch blades down into the base when the lever arm is down.