I use 10" tent stakes from Harbor Freight (they are $3 for 6). Also on some of my larger inflatables i put a 4' metal fence post in the ground with 1" PVC over that. Cap the PVC and drill a hole in the PVC at the same level as the back anchor point on the inflatable. Then I run the cord though the hole in the PVC before anchoring it to the ground. This keeps my 12' Santa standing up in the Oklahoma wind.
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