Our children used to love tinkering with this set of Wedgits (as did any other people who happened to be in our space at the time the Wedgits box was out).
When they were really little we'd do the whole (excellent) Montessori idea, I'd build a shape and they'd copy the building of it ... here's a small funny though >
During some more involved building sessions with 3 yr old Daisy, I was trying to nut out how the pieces went together so that she could "monkey see" "monkey do".
Bobs, 5yrs old, could see marmee was just not getting it, so quietly sat RIGHT in front of me with the pieces needed to make the shape and s.l.o.w.l.y built it while I watched - even then it took me at least 4 goes to get the shapes to lock in place (laugh!). I was not doing well with following 3D instructions - which Wedgits are.
(Great early (? snort) years discovery toy. Our family built with these from ages 2-8.)
Needless to say Daisy mastered Wedgit building from watching Bobs, then they both ending up teaching marmee how to build 'involved' Wedgits.
*WEDGiTS currently can not be purchased in NZ - Australia is our closest distributor.