Could also connect a bunch of locks and put all the keys on a key ring. Lots of pictures of latch, lock, etc ideas for montessori type preschool. This lock one could be made with 2 boards, some o-rings, and some locks from Dollar Store.
The bolts are graded in diameter for a more difficult exercise. Five slotted bolts and stubby screwdriver. Designed by a Montessori teacher to aid the development of eye-hand coordination and teach a practical skill.
Easy and fun.Velcro + popsicle sticks make for great quiet time or restaurant activity. Put velcro dots on the ends of popsicle sticks. Kids can make letters or shapes over and over again. I found velcro dots at my local dollar store.