The Handyman's Pocket Book: Gates - Care Of.

A wood gate needs periodic attention.  Shrinkage allows the joints to open, and any braces that may be fitted fail in their job of keeping the whole rigid.  Thus the framework sags and the fittings get out of register.  Any loose joints should be pulled up tight.  First rub in some thick lead paint, and it the wedges are loose remove them and refis.  See that the cross-brace is close fitting in its joints, and strengthen any weak joints with flat metal plates let in flush and screwed on.  The joints must be pulled up tight first.  When painting, pay particular attention to end grain because it is here that decay generally starts.  It is because of this that joints must be tight since the cutting of joints always exposes a certain amount of end grain.  Sometimes a new part can be spliced on.  Clean the wood back well to beyond the decayed area (see B, Fig. 2) and screw on a new piece, painting the joint.  The mortice will have to be cut into the new piece so avoid putting screws where they will be in the way.

PRESERVATION.  Posts that are set in earth often get out of upright and should be set in concrete after truing up.  It this cannot be done excavate the earth around the post and well ram hard rubble or large stones into the cavity, but in any case treat the lower ends of the posts with anti-rot preparation before doing so.  A time-honoured method of treating posts to be buried is to char the end over a fire and dip into tar.  Creosote is often used, but merely to coat the end is of little value.  The better plan is to immerse the end of the post in a tank of creosote and heat up to about 180 deg. F.  It is maintained at this heat for about an hour and then allowed to cool, the timber remaining in the tank.  It is in the cooling period that the absorption chiefly takes place.  Proprietary preparations such as Cuprinol are also widely used to preserve the timber.

If a closing spring is fitted adjust it so that the gate closes without undue force, and fit a small rubber buffer at the centre of the shutting post; this will make the operation of the gate practically silent.  See that the hinges are in good order, re-adjust the catches and lubricate all fittings.  Any decayed portions should be cut out and new wood spliced on, the joints being well painted and screwed.

The best method of bracing a post is given in Fig. 3, A.  For a narrow gate the main bottom shoe board is sometimes taken across from post to post as in Fig. 3, C.  In any case treat the buried portion with anti-rot compound.

A cheap yet effective way of preventing a post from leaning is that at B.  Two cross-bars are nailed on as shown, the bottom one at the outside, and the top one (a few inches from the surface) at the inside.  Treat to prevent rot, set in rubble, and tamp well.