The simple pins we have discussed had several essential elements, any of which may be absent from the positions you find on the board in front of you. In that case you may be able to create the missing elements or substitute for them. In all the positions so far, for example, the pinned piece made a good target for the piece that pinned it; sometimes that will not be so. In each case there were open lines between the pinning piece and the pinned piece, and between the pinned piece and the king; sometimes this will not be so. In every instance the king and the pinned piece were in a line at the start of the position; sometimes that will not be so. Spotting and rectifying these sorts of obstacles will be our project in the next few sets of studies.
We start with pins that need to be perfected by replacing a target that can bite back with one that is toothless. To the left is the point in simplest form. Start from the Black king and work out along the lines leading away from it. You see that the bishop on d4 is vulnerable to a pin. But it would have to be pinned on the long diagonal leading toward h8; and if a White piece pins it on that line, the bishop will be able to bite back. Thus Bb2 by White leads to BxB+ by Black (followed a move later by RxR). But since Black has left a piece in pinnable position, perhaps White can trade it for a better target by capturing it and pinning the piece that performs the recapture. He plays 1. RxB, RxR; 2. Bb2, and now Black’s rook is pinned. White takes it a move later with BxR.
Now incidentally you may have noticed that White’s rook also exerts a pin against Black’s bishop: if the bishop moves, White has RxR—another example of a relative pin. But White can’t do anything with it. If he goes after the bishop with Be3, Black breaks out of the pin with Bc5+; since the move gives check, White has to spend a move replying to it with BxB—but now Black is the one who plays RxR, winning the exchange. A different way for White to try to take advantage of the pinned bishop would be to attack it with his king—e.g., Kb3. But then Black has Bf6, moving the bishop to safety and using it to guard the rook at the same time.