Always glad to oblige Mike. To paraphrase Law 9, “The bowling crease, is the line the stumps are in the middle of, and is drawn at each end of the pitch so that the three stumps fall on it (and consequently it is perpendicular to the imaginary line joining the centres of both middle stumps). Each bowling crease should be 2.64 m long, centred on the middle stump at each end, and each bowling crease terminates at one of the return creases.”
“The popping crease determines whether a batsman is in his ground, as well as front-foot no balls, and is drawn at each end of the pitch in front of the stumps. The popping crease must be 1.22 m in front of and parallel to the bowling crease. Although it is considered to have unlimited length, the popping crease must be marked to at least 1.83 m on either side of the imaginary line joining the centres of the middle stumps.”
“The return creases are the lines a bowler must be within when making a delivery, and are drawn on each side of the stumps, along each sides of the pitch (so there are four return creases in all, one on either side of both sets of stumps). The return creases lie perpendicular to the popping crease and the bowling crease, 1.32 m either side of and parallel to the imaginary line joining the centres of the two middle stumps. Each return crease ends at one end at the popping crease but the other end is considered to be unlimited in length and must be marked to a minimum of 2.44 m from the popping crease.”