What is a Packer? A packer also called a prosthetic, is any object (sock, silicone, or otherwise) that allows to "sport" a package. Packers can be tucked into snug underwear or placed into a sock and safety-pinned to pants or underwear if you want to try packing without spending cash on specific packing straps. However, there are also underwear-style harnesses, packing straps, and packing pouches.