Boundary Lines

Understanding boundary lines is one of the most fundamental responsibilities of an official. Every decision about in-bounds or out-of-bounds hinges on your knowledge of where players and the ball are in relation to these lines. Mastery here builds confidence, credibility, and consistency.

Endline / Baseline

• The endline (also called the baseline) is the boundary line located at each end of the court.
• The line itself is out of bounds.
• If the ball or a player touches the line, it is considered out.
• The inside edge of the endline marks the boundary. Any part of the foot or ball touching this edge means out of bounds.
• Additionally, if the official is touching anywhere on the endline or out of bounds and the ball touches that official, it is an out of bounds violation.

Official’s Responsibilities

• Know who last touched the ball before it went out. This determines possession.
• Identify the correct throw-in location: it should be at the nearest spot where the ball went out, unless rules direct otherwise (e.g., fouls, violations, timeouts).
• The Lead official typically owns the endline and should maintain clear sight of that boundary while officiating plays near the basket.

Boundary Line Responsibilities for Each Official (Three-Person Mechanics)

Boundary Line Responsibilities for Each Official (Two-Person Mechanics)

Sidelines

• The sidelines run the full length of the court and define the outer boundary of the playing area.