Sometimes he uses them for two dimensional art, like this outline of the state of Missouri.
Other times he builds up. He went through a phase where he'd wath You Tube videos of roller coasters and then build his own--sometimes with the wooden tracks from his Thomas trains and sometimes with Jenga pieces serving as tracks. Last year he entered a highway interchange phase as you can see below.
He's even created his own Jenga font--letters and numbers, so he can track the contestants and points on his favorite show--Fetch with Ruff Ruffman.
I can alway's trace Fritz's activities for the day by following the trail of blocks left behind (they usually travel in groups of four). It's a quiet activity, it encourages imagination, and I don't have to replace batteries all the time. Someday if you find out Schnickelfritz has designed the latest, greatest roller coaster at a theme park near you, you'll know it all started with a set of Jenga blocks.
Be sure to check out the other J posts at Ben and Me.