Regarding some of the comments above, from my biology knowledge, I know that we are trying to tap the phloem (carry sap/nutrients) rather than the xylem (carry water), and both are relatively close to the surface of the tree.
Does anyone have some sensible advice on where to tap (height above ground level, etc) and how deep to go? Are there any features (boles, knots, buttresses) that would help in deciding the tap point?
I have also seen Ray Mears and others either carve a wooden plug or use mud to fill the hole after use. Any comments?