setpart
nounUK /ˈsɛtpɑːt/
US /ˈsɛtpɑːrt/
A setpart is a piece that you keep apart to use with other pieces.
She put each setpart in its own little box.
OTHER MEANINGS
2. A part of a set that can be taken out and used alone.
The wheel is a setpart of the toy car.
3. A small piece that belongs to a group of matching pieces.
He lost one setpart of his train set.
4. A separate piece kept ready for building something.
We sorted every setpart before starting the model.