Blockading Knight
Light square blockade
A multi-purpose term.
As in position 1 (Caruana - Shankland, 2021), it can refer to the practice of impeding a passed pawn by putting a piece, ideally a knight, in front of it. The knight is the ideal blockading piece, as, even blockading, it can still attack by virtue of its unique movement.
Alternatively, it can refer to the defensive control of a colour complex. In position 2 (Reshevsky - Petrosian, 1953), Petrosian's famous exchange sacrifice 25... Re6!! meant that when white captured the rook on e6 it would be replaced by a black pawn that would guard the d5 and f5 squares, thus establishing a light square blockade.
See: 'Colour complex'.