A focus mitt is a padded target attached to a glove and usually used in training boxers

Boxing

Boxing, also called pugilism, is a combat sport in which two people fight each other using their fists. Boxing is supervised by a referee over a series of between one to three minute intervals called rounds...

 and other combat athletes

Combat sport

A Combat sport, also known as a Fighting sport, is a competitive contact sport where two combatants fight against each other using certain rules of engagement , typically with the aim of simulating parts of real hand to hand combat...

.

The person holding the focus mitts will typically call out combinations and "feed" the puncher good counter-force while maneuvering and working specific skills. Focus mitts are often used as an augment to sparring, with more explicit focus on the puncher than the feeder, especially to develop good punch

Punch (strike)

A punch is a striking blow with the fist. It is the most commonly used attack in hand to hand combat. It is used in some martial arts and combat sports, most notably boxing where it is the only type of technique allowed...

 combinations and defensive maneuvers such as "slipping," "bobbing" and "weaving."

When wearing focus mitts it is important not merely to hold them but to actively "feed" them into the punches, to balance their force and prevent injury to both parties.

Similar to a focus mitt but designed for different purposes are heavier thai pads used in muay thai

Muay Thai

Muay Thai is a combat sport from Thailand that uses stand-up striking along with various clinching techniques. It is similar to other Indochinese kickboxing systems, namely pradal serey from Cambodia, tomoi from Malaysia, lethwei from Myanmar and muay Lao from Laos...

 boxing and kicking shields used in a variety of martial arts

Martial arts

Martial arts are extensive systems of codified practices and traditions of combat, practiced for a variety of reasons, including self-defense, competition, physical health and fitness, as well as mental and spiritual development....

to help gauge distance and practice techniques with kicks, knees and elbows.

Working with focus mitts

It is often said that holding focus mitts can be as taxing as striking them. Typically, the person wearing the focus mitts will yell a number that represents a combination. For example, yelling "three!" might signify that the striker should throw a jab, followed by a cross, followed by a hook in rapid succession. Defensive maneuvers are often incorporated into the combinations as well.

Improving punching technique relies upon the person wearing the focus mitts knowing where to set his/her hands, as well as knowing how to time the movement of the focus mitts. Typically the holder will comment on how the striker can improve his/her technique between combinations.