How to replace a ferrule? Replacing a Flexyfoot ferrule is a quick and simple process.First, you will need to measure the diameter of your walking stick or crutch to ensure you have the correct size Flexyfoot. Next, reduce the height of your walking aid by 50mm (if the walking aid is not adjustable then you may have to cut it down to size). Now, separate the foot from the collar by pulling the foot away from the collar until it clicks – then unscrew. Insert the end of the walking stick or crutch into the collar and push it hard. Once securely in place, screw the foot into the collar until it rotates freely and then push the foot until it clicks into place.