Papaw was an Illinois St. Police Lt. back in the 30's & 40's. When I was a kid, he showed me his S&W HD .38/.44 6" and his blackjack.

Three things I still remember was:

1. "Don't hit em' in the head with a blackjack, You'd kill em'. Hit in the collar bone, shoulder, elbow, wrist/hand and you'd break it and the fight would go out of em".

2. Don't ever put your wrist through the blackjack strap. Someone could grab the blackjack and tie up your arm and be unable to use it. Just put your thumb through the loop and wrap the strap around the outside (back) of your hand so it ends up resting in your palm between the thumb and forefinger. That way, if someone grabbed your blackjack, all you had to do was open your hand and the jack would be released.

3. Always use the blackjack with your left hand, so if it doesn't work, you can still draw your pistol with your right hand!