The CEM Anchor (Cañonismo en Mexico) or also referred to as the Mexican recoverable anchor. The CEM is a releasable and retrievable rigging technique which requires no extra gear besides the rope itself. Like some other recoverable anchor systems, when not rigging with a separate pull cord, the CEM requires twice as much rope as the length of your rappel. Unlike the HMS/Rapide method or just wrapping your rope around a tree, this technique does not require you to pull the entire rappel strand up and around your anchor to retrieve. There are also multiple techniques to safety this system when moving with a group of people, although the safety must be removed by the LAPAR (Last Person At Risk) prior to descending.
Practice this in non-vertical environments until you feel proficient and safe.