The Wheel Arm Track Guard fits in the space where the wheel arm moves across to lock when you lift the coop to move it. The wheel arm goes through the comb-like guard, but it prevents any overly curious chickens to put their head through this space. The Wheel Arm Track Guard is included in all Eglu Cube and Eglu Go UP run boxes as standard from July 2021, and if you have an older coop you can buy it here.