Shell Holder
The slotted steel holder on a press ram that grips a case by its rim and holds it aligned while it is sized or has a bullet seated.
A shell holder is a small slotted block that snaps into the top of a reloading press ram and grips the case head by sliding under the rim or extractor groove. As the ram rises, it carries the case up into the die and holds it square so the operation runs straight.
Shell holders are sized to families of cartridges that share a common rim diameter, so one holder often serves several chamberings in a caliber group. Choosing the correct holder for the brass is necessary for the press and reloading dies to work together without crushing or misaligning the case.