Cleco Plier

 A special type of pliers are used to push in the spring-loaded plunger. This pushes down on the step-cut locks, which pushes them away from the spreader bars and allows them to come together. This allows the user to slip the locking jaws through a hole made through multiple sheets of material. When the plunger is released the spring pulls the locking jaws back towards the spreader bar, which separates the two jaws. The material sheets are then squeezed in between the step-cut area and the steel cylinder. This keeps the holes in the separate sheets aligned. Figure 1 shows how it is look like.

(Figure 1)