Righty tighty...more gnats.

Here begineth the lesson...fitting dovetails, part deux.  In compiling this entry, I make the not unnatural assumption that anyone taking the time and effort to read this will be able to cut to a line.  What follows are my own deductions on how this particular joint goes together, but you've probably worked it all out already.

Shown below is a gash off-cut of elm, split into two, with the shoulder lines marked and one dovetail cut, approx 25mm wide.  The shoulder line has been chiseled...I never leave them straight from the saw as the fuzzy edge is simply not accurate enough.

Once the tail(s) has been cut, use whatever method you like to transfer the tail(s) onto the other half to mark the socket(s).  I'm using a Robert Ingham jig here which I made a few years ago.

This, though is where the process gets cunning.  Many people assume that the end of the tail and the surface of the socket board should be flush.

Big, biggy mistake!

Dovetails go together by the shoulder line (arrowed above) pulling tightly against the inside face of the socket board and the only way to make this happen is have the dovetail....

...proud by half-a-gnats.  Once the socket has been cut, the tail should have some easement chiseled onto the inside leading edges...

...so that the joint can then be tested.  You'll find that as the tail is tapped into the socket, the shoulder line on the tail section tends to go backwards by the merest fraction, making the joint very, very tight...almost impossible to go together as the dovetail is now the same fraction larger than the socket.

Difficult to get your head round, but logical eventually!

The way to make the joint fit is to ease the sides of the socket with a wide paring chisel, just enough to remove...

...the saw marks and check to visually see that the sides are dead square.  Never, ever, try to ease the joint by paring the tails themselves...disaster awaits if you do that!
If everything has gone according to plan, you should find that the tail will tap down into the bottom...

....of the socket.  If it's really too tight, then take off just the merest whisper again with the paring chisel.  The joint shown above is unglued and you can see the slight projections which are planed off.

Dovetails seem to be the modern 'Holy Grail' of woodworkers today which is odd to me as there are a lot more difficult, cantankerous bits of joinery out there.

Ask any Japanese carpenter...