This is called diagonalisation . Apart from allowing you some extra safe moves at the end of the game, it is also an essential ingredient in one of the ways used to attack a weak edge. So, if you are trying to decide whether to make a particular move, one thing to consider is what it will do to the main diagonals. If the answer is yes, the move is probably better than an otherwise equally good-looking move which has no such effect on these diagonals. However, it should be stressed that you should not try to diagonalise too early in the game, because in the early stages it is too easy for the opponent to cut accross your diagonal.
Diagonalisation is a ploy best left to the later stages of the game.
To finish, here are two very similar looking positions. In both positions it is Black to play. There is just one difference between these positions. In figure 3, White has managed to use diagonalisation to fool Black. If Black had been more careful and kept a piece on the c6-f3 diagonal then the win would be easy.