Celtic there's a couple of things you could try, put a clip-on ring on his non ring leg and tie a piece of string (about 3 inches) to that and his ring, you do this so he can walk and get about but as soon as he fights he cant get a decent purchase/foothold as hes unable to spread his legs. Another thing you could try is to put a piece of cardboard on the front of his nestbox so he cant see out, this sometimes helps.