The patented Xeros Endpin Anchor is a handy tool for those long sessions. Simple yet effective, it consists of a slip-resistant cup attached to a 2" wide woven strap; at the end of the strap is a large ring -- large enough to easily accommodate a chair leg that is up to 2" wide and deep, square or round -- which can then be placed around the leg of your stool or chair. What's the point? Sometimes, dusty floors or old, worn out rubber endpin caps conspire to give our instrument less than reliable footing - so this unique system keeps the bass from "walking away" from you while playing, or during extended rests. (I've heard of "walking bass" but I don't think this is what they meant!)
Durable enough that the manufacturer offers a lifetime guarantee, so it's made to last. But it's also very light and compact, small enough to fold up and fit easily into the palm of your hand - and therefore, the accessory pocket of your bass bag or your jacket pocket. The strap is adjustable, so you're sure to find the length that is comfortable for you.
This is the most current version, which has a "V-shaped" receiver, which is easier to guide the endpin into than the ring-shaped receiver. It can also be used with the Super Endpin Ball.