You may use any finger (or thumb) with the Fingerprint Reader, however, your index finger of either hand will work best. Always place the pad of your finger (not your fingertip) flat onto the center of the reader’s clear window. Do not “roll” your finger. Apply gentle pressure, similar to pushing a button. Hold your finger on the reader for up to one-and-a-half seconds, then lift your finger. You should press firmly and release. Do not press and hold your finger for an extended period.