Barry -
1. Dig a 4' deep hole - use a 3-point post hole digger
2. Get a 12' piece of logging chain
3. Put chain in hole centering with a pipe - leaving 8' available to connect to ATV/UTV
4. Fill hole with concrete
5. Buy GOOD lock and wrap chain around axle and lock (park the ATV/UTV as close or even on top of the buried chain).
If thieves are determined, they can cut the lock or the chain with a hydraulic cutter, but they won't be able to cut with handheld bolt/wire cutters AND the concrete will not move. If they are REALLY determined - they are going to get it regardless of what you do.
