Hog Ring Pliers are special pliers that make it easier to install hog rings. Hog rings are used in the DeLorean to hold the covers on the seats. Although you can make due with a pair of needle nose pliers, it is much easier to use the proper tool when installing hog rings.
Hog ring pliers can be found at a variety of shops, from upholstery stores to the Hover Fence Company. Such stores also often sell the hog rings you'll need to install new seat covers.