Thought I'd share an ingenious method for anchoring patio mat corners that I learned at a ham radio gathering being used to anchor antenna mast guy lines - lag bolts (with fender washers) drilled into the ground. No tripping on stakes and quick/easy in & out.
For the guy lines, I use 3/8" x 8" lag bolts; for the mat corners - 6" long do fine.
It's probably obvious to some that the pic was taken near Quartzsite, AZ - where there the soil consists of rocks, more rocks and a little dirt.