Does anyone know what these plastic sewing notions are used for?

A friend posted how she is going through her mother’s old sewing basket, and came across some rectangular pieces of hard plastic. I seem to remember seeing something similar in my grandmother’s sewing basket, but I never knew what they were for.

Does anyone know what they would be used for?

Some sort of stay? A template for quilt blocks?

They look like dividers for the white plastic tray in the first photo. See the grooves in the tray? Those slide in to divide it up into custom sized compartments.

Nice catch! I’m going to ask her about that.

Yep, dividers.

Thank you! They are indeed dividers. I appreciate everyone’s help.

The irony here is that below the hand holding the unused dividers you can see a one such divider actually being used as intended.