Ah, Mr. Nettles. I've seen this episode twice now, and as it reaches the part where the inspector hauls out a theodolite to check a sight-line I cringed for the second time. John, if the necessity should ever occur again in your acting career, that you have to set up a theodolite, please take a 5 minute lesson from a surveyor or a construction site engineer. All the best. N.P.Lawton (Civil Engineering Instructor at Fanshawe College, London ON, Canada)(Retired) That's all I want to say, but the powers that be are insisting on ten lines and a summary. I don't want to do either of those things. In order to prove the alignment, the theodolite would need to be carefully placed in a particular spot, or "over-lined" to get an exact line. and the plate has to be levelled in two directions at right angles to each other using the three thumbscrews on the levelling head. Hope it's long enough now NPL