A good boat chock is intended to turn the direction of a line and prevent chafing. Good chocks should have round metal with no edges that can fray the line! Jamestown Distributors carries straight and bow chocks.
Straight chocks are available in stainless steel and silicon bronze for corrosion-fighting purposes. These are to be used where line is coming in straight, like stern or midships. You will need two screws to install (not included).
Bow chocks are available in stainless steel. Designed for use at the bow or anywhere line comes in at an angle.