We used small building blocks, shaving cream, and plastic knives for building.  In a few books children have discovered that builders use mortar between bricks to keep them together to create houses and walls. 
While building the children had so much to say! Here are some of their comments on describing what they were building:
“I made  house with a window.” Javier
“I gave it a roof!  It has a garage.  You get into your truck, then go out the garage. “ –Steven
“It will fall without the shaving cream!” –Biannett