"acorn" is the head of the "pintle" or pin that
passes thru the knuckle. Sizes of butts are indicated in inches for
length, and as "narrow," "middle," "broad" and "desk" for width.
The pin may be either riveted into the knuckle as in box-hinges or
removable as in door-butts. Sometimes, as in blind-hinges, the pintle
is fastened into one knuckle, but turns freely in the other.

A butt-hinge may be set in one of three positions, Fig. 235: (1) Where
it is desired to have the hinge open as wide as possible, as in a
door. Here the knuckle is set well out from the wood. (2) Where it
is desired to have the hinged portion open flat and no more. Here the
center of the pin is in line with the outside surface of the wood.
This is less likely to rack the hinge than the other two positions.
(3) Where it is desired to have the knuckle project as little as
possible.

[Illustration: Fig. 234. Parts of a butt-hinge. 1.1. Leaves. 2.2.2.
Knuckle. 3. Pintle. 4. Acorn.]

HINGING

In setting the hinges of a box cover, first see that the cover fits
the box exactly all the way around.

In the case of a door, see that it fits its frame, evenly all the
way around, but with a little play. To insure a tighter fit at the
swinging edge this edge should be slightly beveled inwards.

In attaching a butt-hinge, the essential thing is to sink the hinge
into the wood, exactly the thickness of the knuckle. The gains may be
cut in one or both of the pieces to be hinged together.

With these matters determined proceed as follows: In the case of a box
cover, the hinges should be set about as far from the ends of the box
as the hinge is long.

In the case of an upright door, locate the hinges respectively above
and below the lower and upper rails of the door. Mark with the knife
on the edge of the door the length of the hinge, and square across
approximately the width of the gain to receive it. Do this for both
hinges. Between these lines gage the proper width of the gains. Set
another gage to one half the thickness of the knuckle and gage on the
door face the depth of the gains. Chisel out the gains, set the hinges
in place, bore the holes, and drive the screws. Place the door in
position again to test the fit. If all is well, mark the position of
the hinges on the frame, gage and cut the gains, and fasten in the
hinges. Where the hinge is gained its full thickness into the door,
no gain, of course, is cut in the frame. If the hinges are set too