This section is from the book "Pictorial Practical Fruit Growing", by Walter P. Wright. Also available from Amazon: Pictorial Practical Fruit Growing.
Pears are comparatively easy to prune, for they do not present the great variations which have been noted as occurring in Apples. The twelve-cordons-on-a-tree type - i.e. specimens with a limited number of branches trained well apart, the breastwood pruned to six leaves in August, and spurred to a couple of eyes in winter, or before growth starts in spring - is the most healthy and productive.
N.B. - ln pruning Pears - and, indeed, all classes of fruit - avoid leaving stumps or "snags." A "snag" is the portion of shoot, ranging in length from 1/2 inch to 2 inches, which many pruners leave on each piece of growth which they cut. Such stumps are a source of danger to the tree, as they inevitably decay. The cuts should be made with a sharp knife close to the bud, then no "snag" is left. (See Fig. 11, and Fig. 12.)

References
A, shoot cut in advance of the bud, leaving a snag, a: b, proper direction of cuts.
C, cut made on same side as bud, leaving a short snag, e: f, proper direction and place.
D, cut made partly below the bud, g, resulting shoot; not good.
H, oblique shoot shortened to top side bud, m, to secure a straight branch, n.
I, top of pyramid: o, leader shortened; p, new leader; q, side shoots; r, side shoot shortened to outside bud, right; t, shoot shortened to inside bud, wrong; s, u, resulting shoots.

References
A, portion of an extending branch: a, continuation or extension shoot, to be trained in its full length in the case of a tree extending on an espalier or wall; b, side shoots to be laid in (in the case of a fan-trained tree) if required for furnishing the space properly with branches, otherwise they should be pinched to three good leaves (not counting basal ones) to form spurs (sec C); c, short shoot terminated by a large, somewhat rounded bud, not to be stopped; d, natural spurs - short, stubby growths, terminated by a corona of leaves and with a prominent central bud in the centre of each - usually a blossom bud.
B, natural spur: e, previous year's wood; f, current year's growth; g, central bud from which fruit is produced in the Pear,
C, shoot (such as b in A) pinched to form spurs: h, previous year's wood; i, small basal leaves: j, good characteristic leaves; k, point of stopping the shoot; l, laterals stopped at second joint; m, sublaterals pinched to one leaf; n, point of shortening at winter pruning.
 
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