Squeezing a too-fat component into a too-skinny dado or groove
Now you've done it. For whatever reason, your board or panel is too thick to fit into the dado or groove you cut for it. If the ends of your dadoes or grooves won't be visible after assembly, the answer's simple.
Use a thin-kerfed oriental handsaw…thin kerfed table saw blade…thin, slot-cutting router bit… bandsaw…or scroll saw to cut the thinnest-possible kerf down the length of the edge that's to be glued into your dado or groove.
Use sandpaper or a file to chamfer the edges…apply glue…and tap your workpiece into your groove or dado with a wooden mallet. Your thin kerf should allow the wood to flex enough to slip into position with just a little coaxing.