The technique is 6 deeply buried concrete tie down anchors per glider
- nose, tail and two on each wing - one inboard and one outboard. On
flex-winged composite gliders, wing stands are used. The gliders are
oriented 90 degrees to the high-wind direction.

I'll never understand how somebody would tie down a plastic glider
outside rather than put it in the trailer. Rigging a modern glider is a
matter of 10 minutes but possibly worth a couple of thousand dollars.