"RickH" wrote in message
If it's wood I'd just squirt some waterproof wood glue deep into the
crack and "C" clamp it tight overnight (a clamp every 6 inches or
so). The glue bond will be stronger than the original material was.
Let the oozing dry too then just cut that off with a sharp chiesel or
block plane once it's hard, (if you try to wipe the glue ooze while
it's wet it will just seal the pores and make the surface impossible
to stain later).

Only thing I'd do different is to first drill a small hole at the top of the
crack. That can prevent it from traveling further. Once you do that, you can
even spread the crack a tiny bit to bet the glue in easier.