I don't know about you but I have a hard time drawing a straight line and I have to erase a lot while drafting, This nifty gadget will solve all of your 4'' line drawing and erasing needs! This holds a standard poly eraser you can find at any school or hobby store. This design also has a fold out straight edge and a spacer that will hold the eraser up as it gets smaller after use.I printed this on a Rep2, med quality, 10% infill, no support, raft. after printing I used a wooden tooth pick for the hinge, little bit of sanding. place the spacer in before the eraser. To make it easier to push in the eraser wet it then push it in and let it dry, it should be a tight fit so it will stay in place.