I didn't have any heavy wire (or was it I couldn't find wire cutters!). But, string held in place with canes, works for us one year (before going to the raised beds). I think I had early broadies under, then moved to protect an early planting out of dwarf french beans. ;D
They worked better than the cheap polytunnel cloche thing that was in Lidl's that someone on here mentioned (2 years ago?) which blew away. I think I still have an unused one (or is it just the empty box) in the shed!