I've been mulling over the two issues raised in this thread - scribe lines on dovetails and 'piston fit' drawers - and made a realisation; my old woodwork teacher at school knew what he was talking about!
I was taught 30-odd years ago that when making traditional drawers the back piece should always be cut a millimetre or so short in its length, giving the whole drawer a very slight taper from front to back.
If the drawer front is cut ever so slightly too long, this enables you to plane the sides at the joints to get a perfect fit, simultaneously removing the scribe lines from the dovetails. It also means that that the drawer is very unlikey ever to bind, whatever the change in atmospheric conditions, as there is sufficient clearence along the length of the drawer with the 'perfect fit' only being at the very front where it is visible.
The other thing I was taught was to make the drawer back around 10mm lower than the drawer sides. I can't remember the explanation given for this but I now see that it eliminates completely the 'piston' problem. Air is able to escape into the drawer box and then out through the opening as the drawer is pushed in, a seal made only at the last moment.
I have been making drawers this way ever since. To be honest I just assumed that everyone else did too.
Evidently not!
:lol:
Cheers
Brad