(a) Before the toss the umpires shall agree the boundary of the field of play with both captains. The boundary shall if possible be marked along its whole length.
(b) The boundary shall be agreed so that no part of any sight-screen is within the field of play.
(c) An obstacle or person within the field of play shall not be regarded as a boundary unless so decided by the umpires before the toss. See Law 3.4 (To inform captains and scorers).
2. Defining the boundary - boundary marking
(a) Wherever practicable the boundary shall be marked by means of a white line or a rope along the ground.
(b) If the boundary is marked by means of a white line,
(i) the inside edge of the line shall be the boundary edge.
(ii) a flag, post or board used merely to highlight the position of a line marked on the ground must be placed outside the boundary edge and is not itself to be regarded as defining or marking the boundary. Note, however, the provisions of (c) below.
(c) If a solid object is used to mark the boundary, it must have an edge or a line to constitute the boundary edge.
(i) For a rope, which includes any similar object of curved cross section, lying on the ground, the boundary edge will be the line formed by the innermost points of the rope along its length.
(ii) For a fence, which includes any similar object in contact with the ground but with a flat surface projecting above the ground, the boundary edge will be the base line of the fence.
(d) If the boundary edge is not defined as in (b) or (c) above, the umpires and captains must agree before the toss what line will be the boundary edge. Where there is no physical marker for a section of boundary, the boundary edge shall be the imaginary straight line on the ground joining the two nearest marked points of the boundary edge.
(e) If a solid object used to mark the boundary is disturbed for any reason during play then, if possible, it shall be restored to its original position as soon as the ball is dead. If it is not possible then,
(i) if some part of the fence or other marker has come within the field of play, that part shall be removed from the field of play as soon as the ball becomes dead.
(ii) the line where the base of the fence or marker originally stood shall define the boundary edge.
3. Scoring a boundary
(a) A boundary shall be scored and signalled by the bowler’s end umpire whenever, while the ball is in play, in his opinion,
(i) the ball touches the boundary, or is grounded beyond the boundary.
(ii) a fielder with some part of his person in contact with the ball, touches the boundary or has some part of his person grounded beyond the boundary.
(iii) the ball, having crossed the boundary in the air, is first touched by a fielder who has not satisfied the conditions in 4(i) below.
(b) The phrases ‘touches the boundary’ and ‘touching the boundary’ shall mean contact with either (i) the boundary edge as defined in 2 above or (ii) any person or obstacle within the field of play which has been designated a boundary by the umpires before the toss.
(c) The phrase ‘grounded beyond the boundary’ shall mean contact with either (i) any part of a line or solid object marking the boundary except the boundary edge or (ii) the ground beyond the boundary edge or (iii) any object in contact with the ground beyond the boundary edge.
4. Ball beyond the boundary
After it has crossed the boundary in the air, a ball may be caught, subject to the provisions of Law 32, or fielded provided that
(i) the first contact with the ball is by a fielder, not touching or grounded beyond the boundary, who has some part of his person grounded within the boundary or whose final contact with the ground before touching the ball was entirely within the boundary.
Any fielder subsequently touching the ball is not subject to this restriction.
(ii) neither the ball, nor any fielder in contact with the ball touches, or is grounded beyond, the boundary at any time during the act of making the catch or of fielding the ball.
The act of making the catch, or of fielding the ball, shall start from the time when the ball first comes into contact with some part of a fielder’s person and shall end when a fielder obtains complete control both over the ball and over his own movement.
5. Runs allowed for boundaries
(a) Before the toss the umpires shall agree with both captains the runs to be allowed for boundaries. In deciding the allowances the umpires and captains shall be guided by the prevailing custom of the ground.
(b) Unless agreed differently under (a) above, the allowances for boundaries shall be 6 runs if the ball having been struck by the bat pitches beyond the boundary, but otherwise 4 runs. These shall be described as a Boundary 6 and a Boundary 4 respectively, although the number of runs awarded may not be 6 or 4 if other allowances have been agreed under (a) above.
These allowances shall still apply even though the ball has previously touched a fielder. See also (c) below.
(c) A Boundary 6 will be scored if and only if the ball has been struck by the bat and pitches beyond the boundary. The ball is to be regarded as pitching beyond the boundary even though before it has pitched, a fielder
(i) catches it within the boundary but either has some part of his person touching the boundary or grounded beyond the boundary when he catches the ball or, after catching it, subsequently touches the boundary or grounds some part of his person beyond the boundary while carrying the ball but before completing the catch.
See Law 32 (Caught).
(ii) comes into contact with the ball in the circumstances of 3a (iii) above. (d) The award for all other boundaries scored under 3 above, for which either the ball was not struck by the bat or did not pitch beyond the boundary as defined above, will be a Boundary 4, including a case under 3(a)(iii) when the ball has pitched within the boundary before contact with the fielder.
6. Runs scored
When a boundary is scored,
(a) any runs for penalties awarded to either side shall be scored.
(b) the batting side, except in the circumstances of 7 below, shall additionally be awarded whichever is the greater of
(i) the allowance for the boundary
(ii) the runs completed by the batsmen together with the run in progress if they had already crossed at the instant the boundary is scored.
(c) When the runs in (ii) above exceed the boundary allowance they shall replace the boundary for the purposes of Law 18.12 (Batsman returning to wicket he has left).
7. Overthrow or wilful act of fielder
If the boundary results from an overthrow or from the wilful act of a fielder the runs scored shall be (i) any runs for penalties awarded to either side and (ii) the allowance for the boundary and (iii) the runs completed by the batsmen, together with the run in progress if they had already crossed at the instant of the throw or act.
Law 18.12(b) (Batsman returning to wicket he has left) shall apply as from the instant of the throw or act.