Section 49A(1) in The M.P. Nagarpalika Nirvachan Niyam, 1994
(1)Every voter about whose identity the Presiding Officer or the Polling Officer, as the case may he, is satisfied, shall allow his left forefinger to be inspected by the Presiding Officer or Polling Officer and an indelible ink mark to be put on it as far as possible just below the root of the nail so that the ink also spreads on the ridge between the skin and the root of the nail.