It turns out for young hands to be surprisingly difficult to use a screwdriver. The blade has to be held in the slot without slipping out, a normal force applie

It turns out for young hands to be surprisingly difficult to use a screwdriver. The blade has to be held in the slot without slipping out, a normal force applied along with a twisting one. After a while one learns to spin the screwdriver with the fingers while keeping it in the slot. Not to mention the feel of getting the tiny nut threaded on to begin with. It takes the kids a while, and they get frustrated. Legos have the appeal that such skills are not necessary.