#Theoretical

The foundation of all pawn endings — when one extra pawn wins, when it draws, and the geometric concepts of key squares and the rule of the square that decide every case in three rules of thumb.

The canonical winning technique in king-and-rook-and-pawn versus king-and-rook — when the pawn has reached the seventh rank, the defender's king is cut off, and the attacker must build a bridge to shelter from rook checks.

The defensive cousin of the Lucena — how the weaker side draws king-and-rook against king-and-rook-and-pawn when the defender's king is on the queening square and the rook can hold the third rank.

The defensive method that holds rook-and-pawn against rook when the pawn is a rook pawn — the case where the Lucena method fails and the Philidor needs reinforcement.