"Sling" in the context of a porn video tag usually refers to "sling shot", which is a BDSM sex toy used for bondage, spanking or flogging purposes. It consists of a flat, usually leather, strap that wraps around a person's body and has metal rings on each end, allowing for attachments of restraints, whips, or other BDSM toys. The sling provides control and security for the submissive partner, keeping them in place for intense sensations and deep penetration