I tried tapping checks on with a mallet before running them through the sizing die when I started out. In my admittedly limited experience it was tedious and inconsistent. Now I just hold the check under the bullet base as I run it into the NOE sizing die, letting go when the bullet first touches the die. The check has enough play between the sizing rod and the bullet base to line itself up properly and then the force of sizing the bullet seats the check before it enters the die.