I saw an eBay add for those simple cable router knobs listed at one piece for $10. Laughable. I have two six packs of them and each pack was about $10. Anyways, mounted the pencil with two of them onto the outer silicone cover from Apple. Test folding the case so the knobs don't hinder any angles thatvitnfolds. Best to turn each of them about one degree inward or outward from a straight line to put just a touch of pressure on the pencil to help keep it from slipping. The pencil fits snug, so this is precautionary.