This is a large bloody sheet used for multiple scenes in the film, this sheet is covered with blood and has been packed away with several other items since filming wrapped up in 2003.
This sheet was first used in the scene where Andy (Mike Vogel) is being chased through the clothes lines by Leatherface. Leatherface cuts his leg off with his Chainsaw and blood splatters onto this sheet. The same sheet was later used to wrap Andy's severed leg in and take it into the house but the scene was later deleted from the film.