Willie Ryan's classic Tricks Traps & Shots of the Checkerboard, presented here in a new electronic edition, is up to the sixth installment. Here's what Willie has to say on page 16 of the book.

'The issue is clearly drawn in Example 11. The white king on square 22 has a strangle hold on black's pieces on squares 13 and 29, but the black king on square 1 is threatening to go 1-5 next, followed in order by 5-9 and 9-14, and then releasing his impounded pieces by squeezing 14-17, thus driving the white king on square 22 from its potent position. The proposition, therefore, is for white to maintain control of square 22 by preventing the black king on square 1 from effectively advancing up to square 14. This is artistically accomplished by the "shift and stem" principle. It's easy to master these tactical "killers" with step-by-step study.
And now we come to one of the most common of all tactical tricks--- the ever useful pinch play. As the term suggests, a pinch is a move that puts pressure on an opposing piece so that it cannot avoid capture, whereas in a "squeeze" play the threatened piece can avoid capture by moving to an adjoining square. All checker strategy is premised on force, carried out by tactical devices, and the pinch and squeeze are two of the most frequently employed weapons of the adroit tactician. Example 12 is a sparkling illustration of a delayed pinch, wherein white eventually forces black to lose a piece (and the game) by a perfectly timed pincer.'

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Solutions

Example 11 28-24, 1-15, 24-19, 5-9, 19-15*, 9-14, and now the old one-two shift by 22-26*, 14-7, 26-22, beats black, though a piece ahead!

Example 12 32-27, 9-14, 25-22, 6-10, 29-25, 10-15, 27-23*, 20-24, 23-19---the pinch that hurts; white wins.