Pretty sure the function is the same regardless of size. The vernier scale is double-sized; 1.000" measured is 2.000" on the Sorenson scale. Pretty simple (but ingenious) device. Start with the LH side at 0.000", measure the distance between the holes on the inside (or outside would work too, just have to do the opposite on the second measurement). Then slide the LH stop from zero to the RH which now starts your next measurement at "where you left off". Do the 2nd measurement and because the scale on the Sorenson is 2X, you are reading the total of the inside and outside dimensions divided by two. Pure genius!
Bruce