A fap sack is a homemade masturbation device that consists of two materials, those being a zip-lock sandwich baggie and lotion of the user's preference. Another requirement to use this device is that one must have a bed with a mattress and box springs. To use it, the user simply deposits a generous portion of his favorite lotion into the baggie, seals the baggie and spreads the lotion on the inside of it, and inserts the baggie between the box springs and mattress of his bed with the zip side visible. Lastly, the user then inserts his penis into the baggie and thrusts himself in and out of the baggie until climax.
Josh: "Dude, I just found a used fap sack in Brandon's bathroom that he forgot to throw away..."
Nathan: "Aw, sick!"
Nathan: "Aw, sick!"
by Hobo with a shotgun June 17, 2012