Turning coach bolt

[spike237]

I bought a large garden swing. self assembly. Most of the fixings are BZP coach bolts, I needed to tighten them up after a few weeks as the treated wood dried out, but some of them are turning, where the square neck has turned in the wood and is now impossible to tighten up the nuts. Any one got a tip to hold them securely so I can tighten up the nuts.
Concord one for you?

[sddsddean]

In my experience the best thing to do is replace them with normal bolts fitted with a suitable washer. At least you can put a spanner on the end of them then.

[Iggle Piggle]

If its possible with the design, file flats on the round head and clamp mole grips on them. You will have to file little access notches in the wood either side of the bolt head.