If you anchor a lot when fishing, the anchor line can become twisted and unmanageable from the ground tackle spinning on its way to the bottom. To avoid this problem, add a swivel to your anchor. Swivels range from the galvanized-steel Acco (about $58) to the stainless-steel Kong Swivel Anchor Connector (about $85 for ¼-inch chain).
My favorite is the stainless-steel Suncor Universal Anchor Swivel (about $153). Fastened between the anchor and chain, it has a ball-bearing universal joint that lets the swivel pivot as it traverses the roller. Make sure you secure the cross pins with the supplied thread adhesive.