Carman, early in WW II, I believe it was 1941 the Army devised a system of medical classification for soldiers. It was called PULEMS and was brought in to use because the old system was not flexible enough. All the jobs in the army were assigned a PULEMS profile with numbers running from 1 to 5 in each catagory. The catagories were; Physical, Upper extemeties, Lower extremeties,
Eyes/Ears, Mental, Stability. An Infantry man would normally be 1s across the board but a 2 correctable was acceptable for a man who wore glasses.
A soldier with flat feet would not be suitable for the infantry, but could be a driver in the Service Corps, or maybe a mechanic in RCEME.