First problem: markers keep detaching and falling out. Absolutely annoying. Second question: none of the squares are correct. There was a problem with the tension screw that holds the ruler. I can get them to work a little if I go to the surface panel and lean it against the block. The problem is who the hell has time for that. Unfortunately, my return deadline just passed, so I basically have two seventy dollar lines. Squares are complete bullshit. Spend a little more and have Starrett.