When does a touch on the rim make the throw a failure?

• Getting in: the commentary says there is no restriction on how or from which direction the athlete enters the circle.
• The stationary start: "an athlete shall commence their trial from a stationary position inside the circle".
• What stationary means: the commentary says both feet are in firm contact with the ground inside the circle at the same time, with nothing touching the top of the rim or the ground outside, for long enough for the judges to see. The arms and the rest of the body need not be still.
• The inside of the rim: "An athlete is allowed to touch the inside of the rim."
• The stop board: the athlete may touch its inner side. Touching any other part of it is a failure, and the top edge counts as the top.
• The failure: after stepping into the circle and beginning the throw, touching "with any part of their body the top (or the top inside edge) of the rim or the ground outside the circle".
• The first turn: it is not a failure if the touch happens "during any first rotation at a point completely behind the white line which is drawn outside the circle running, theoretically, through the centre of the circle". This is for athletes who spin.
• Loose things: a touch by a loose shoelace or piece of clothing is not a failure. Nor is a touch by something, such as a cap, that was on the athlete at the start and came off.
• Stopping: provided no rule has been broken, the athlete "may interrupt a trial once started, may lay the implement down inside or outside the circle" and may leave the circle. All of it has to fit inside the time for the trial.
• The flags: a judge raises a white flag for a valid throw and a red flag for a failure.

The circle is the whole of the athlete's working space, and the rim is where it ends. A foot braced against the inside of the rim is still inside. A foot on top of it has gone past the edge. The standing start stops an athlete running into the circle to carry extra speed into the throw.