Squash is a fast paced game that must follow a prescribed set of agreed upon rules in order to keep the players safe, and to ensure a fair outcome to the competition. The World Squash Federation is the authority for the rules of the game, and publishes the definitive rule books for the different variations on the game: Singles, International Doubles, Hardball Doubles, Squash 57 (formally Racketball). WSF Rules of Squash
The terms LET and STROKE refer to calls by the marker or referee concerning interference during the rally. While covered in great detail in section 8 of the WSF Singles Rules this simplified decision chart from the College Squash Association should be added to the scoresheet clipboards for quick reference.