Wood biscuits can swell in a humid shop to the point that they won’t fit in a biscuit slot. To fix that problem, I created this biscuit-sanding jig from a couple of pieces of oak scrap.
I cut a biscuit slot in each piece along the stock’s edge, then glued them together to create a holder for the swollen biscuit. I made the slots in the jig slightly shallower than a biscuit is thick. Now, when I run across a swollen biscuit, I drop it into my sanding jig clamped in a vise. A few swipes with a 60-grit sanding block over the biscuit reduces its thickness so it fits the slot again.