Priming
Seating a fresh primer into the cleaned pocket of a case, the ignition step of building a handloaded cartridge.
Priming is the step where a new primer is pressed into the primer pocket after the old one is decapped and the pocket cleaned. The primer must sit flush or just below the case head and bottom out squarely in the pocket, because seating depth affects how consistently it ignites.
Handloaders prize the feel of this step above almost any other. A hand priming tool transmits the resistance of the primer bottoming out, so you can seat each one to the same depth by touch. Even, fully seated primers give uniform ignition, which shows up downrange as lower velocity extreme spread.