Loose piece of a pattern which is attached to the pattern during molding, remains in the mold during lift-off and is only then removed separately.
It is used for undercuts if the mold joint cannot be positioned in this cross section. A good loose piece has a dovetail guide; its precise position can also be secured by means of screws or pins depending on the size and grade of the pattern.
Disadvantages of loose pieces include the additional work for the molder, possible damage to the mold during lift-off, jamming of the guide, premature wear and possible ramming errors during molding. Therefore, loose pieces should be avoided, e.g. by using outer cores.
In the same way, attachments are used for gravity dies and pressure dies. They are used for demolding undercuts.