Hold to toggle 3D Snap. But hold Shift+S to temporarily disable ALL snaps while moving an object. Release to snap again.
If your scene crashes, you don't have enough RAM. Convert trees and cars to (or Corona Proxy). This loads the geometry from the hard drive, not RAM. 3ds max tips
Want to connect two holes or two sets of edges? Select the border edges of both holes and press (Bridge). This works 10x faster than Cap + Extrude. Hold to toggle 3D Snap