Noddy
Importantly - the wedge should run ninety degrees to the grain of the MORTISE piece. Otherwise the wedge can split the timber.
Hope this helps
Philly
Thanks guys. I understand that the wedge should be at 90 degress from the tenon but my question is when you're cutting the wedge does it matter which way the wedge's grain runs?
Noddy
You want the wedges grain to be straight - you'll be tapping it with a hammer so if the grain is short it will splinter.
Is that what you mean?
Philly