In The Optional Finisher (Stacker & Stapler - Samsung ML-6512ND User Manual

In the optional finisher (stacker & stapler)
Paper jam in front of the finisher
Click this link to open an animation about clearing a jam.
1. Open the finisher's rear cover.
2. Open the machine's rear cover.
3. Locate the jammed paper and remove it. The jammed paper might
be inside the finisher or the machine. To avoid tearing the paper, pull
it out gently and slowly.
4. Close the finisher's rear cover and machine's rear cover.
Paper jam inside the finisher
Click this link to open an animation about clearing a jam.
1. Open the finisher's rear cover.
Troubleshooting_ 80