Hi all when we go through canal tunnels I have a problem with catching the corners of our roof on the tunnel sides I have tried to keep away but the boat seams to want to go to the wall ,so I have bought 4 trolley wheels which iam going to fit to the sides of each corner of the boat so I should keep me away from the sides of the tunnel where it curves round ,the tunnel wall was ripping off our bunge clips ,and ripping our cratch cover on the corners , should work with a bit of look ps only £7 for 4 of eBay