Some 5 or 6 years later, they are all still standing up as they were placed. The few times that the pond was fished, they were definitely magnets. I don't have CC (that I know of).
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The holes at the tops were drilled with a 1/2" drill + bi-metal hole saw cutter blade. You don't want to drill thru the tread cuz the steel cords will shut you down toot-sweet. In fact, you have to be careful on the location of the sidewall; too high and you will catch the edge of the steel cords. You will know right away when you start the hole.
I used a 3/8" standard bit to drill the holes for tying them together with UV resistant grade zip ties....the large/long heavy duty ties. Still holdin' today.