This was a really fun little project to figure out
Speedweve was marketed as “Lancashire’s smallest loom” in the 40s and 50s - used for making darning faster and neater.
There were a few different brands of the same type of mechanism consisting of a flat wooden mushroom and a strange metal contraption filled with hooks. Fabric to be mended was held on the mushroom with an elastic and another elastic then fastened the metal bit to the fabric mushroom combo. The hooks hold the top end of warp threads. Flipping the hooks back and forth act like raising and lowering a heddle for a weft thread on a darning needle. You can read more about how they work here.
Vintage Speedweves are the darling of the visible mending movement; the results are much stronger than a fabric patch and can be very decorative.
In the “in use” photos below I hadn’t perfected the hooks yet and I need a lot more practice getting my stitches straight but it works and makes mini weaving go super fast.