Hood loops are used as vehicle anchor points for bow and stern tie-downs while transporting your kayak.
They work as a wedge when the hood or trunk/hatch of the vehicle is closed with the hose end inside and the strap hanging, exposed, outside of the vehicle.
YOU SHOULD ALWAYS USE BOW AND STERN TIE-DOWNS WHEN TRANSPORTING YOUR KAYAK.
When installing hood loops, it is important to wedge the hose between metal parts of the hood or trunk/hatch lid and the body of the vehicle whenever possible to avoid slippage of the hood loop during use.
Also make sure there is adequate space for hood and trunk/hatch hinges and other parts of the vehicle to avoid damage to the vehicle and hood loop.