Strange sewing gadget

Hi everyone! Still going through Granny and Great-Granny's stuff, and in the sewing baskets, I have found many odd things. These small metal ufo's have a little knob on top, that when you turn it, the pins extend. Does anyone have any idea what these are? It's driving me insane! I have asked my Mom, but she doesn't recall ever seeing them in use and has no idea what they're named. I know Granny was an avid embroiderer, so possibly something to do with that? (I still have some of her work, including many cloths that have the pattern and very little or no embroidery done. Sadly, my embroidery skills are non-existent)