The fuser is what melts the toner to the paper.
Over time, the fuser’s wax rollers can become cracked, causing poor image quality. Typically, these cracks are caused by severe paper jams. Paper clips or staples can also destroy fusers.
Pay attention: The fuser can get very hot. Give the printer adequate time to cool down before changing the fuser, and wear gloves if needed.
A fuser is held in usually by four screws, which are easy to remove. Before doing that you have to remove also printer coverings. However, you may need to remove the toner cartridge and several rollers before you can get to the fuser. Of course, this varies among the different models of printers. Just remember to watch out for the heat and make sure that you put the printer pieces back together in the correct order when you're finished.
Disclaimer
Do it at own risk.
