Hi I imagine this is a very stupid question but please bear in mind that I am a complete amateur. I am preparing to try my first mortise & tenon joint with a small shelving unit and I was just wondering why the tenon can't be left the same thickness as the rest of the shelf? I see that the general rule seems to be to make it a 1/3 of the thickness but I don't understand why and I would be happy to leave the tenons at their current thickness if it isn't going to weaken the shelf. Thank you in advance for your time Best wishes Ian

What's the best way to bore the hole thru.