Learn the overhand: an arc instead of a straight, knuckles on target, lead hand up. With a clear note on what federation sources and studies do not show.
The overhand is a cross that does not go straight but arcs from above over the opponent's guard. The most important thing first: in the world federation's material and the Swiss coach education I read, the overhand does not appear [1][2], and I found no study on this punch. What you read here is gym knowledge built on the cross, and where I have no source it is marked as practice.
How hard is it really? The overhand is a cross with a bigger arc, and that is exactly what makes it tricky: the arc makes it slower and easier to see. For straight punches the Swiss material names the wind-up as a mistake, announcing the punch and costing guard [2]. In the overhand the risk lies in the construction. Realistically you need several weeks until you throw it with control (rule of thumb).
And what for? Against taller opponents the handbook recommends moving into shorter distance and working with hooks and uppercuts [1]; the overhand is not mentioned there. That it is especially strong against taller opponents, as some gyms say, is gym knowledge, not proven. What is proven is the foundation: in a measurement on ten amateur boxers the cross produced the highest punch force of all six punches tested, about 1475 N, roughly 150 kg, and rear-leg force was decisive [4]. In boxers the peak speed of the cross was also linked to the position of the body's centre of gravity in the forward-backward direction [5].
Before you build the arc, the cross has to work: hip and torso rotation, weight onto the lead leg, lead hand up, chin down, return along the same path [1]. The handbook names "punching without rotating body" as the first mistake [1]. Milestone: ten clean crosses, after each you stand balanced in the stance.
The overhand starts like the cross. But the fist does not go straight to the target; it travels from the punching shoulder in an arc forward and slightly downward (practice). The wrist stays straight, the palm faces down on impact. The lead hand stays at the chin. Milestone: ten slow-motion arcs, the lead hand does not drop, the head stays behind the shoulder.
The Swiss material requires every punch to land with the knuckle area [3]; shortly before the target the fist is closed and the wrist tensed [3]. The federation's rules list hits with the open hand, the inside of the glove, the wrist or the side of the hand as fouls [1]. With an arcing punch the danger of landing with the side instead of the knuckles is big. Milestone: ten punches on the pad, all land with the knuckles.
Your partner holds the pad a bit higher and at an angle. You throw the arc without pulling the fist back first. The Swiss material explicitly names the wind-up as a mistake [2]. Milestone: ten overhands, no wind-up, return to the stance.
After the overhand you stand with your body turned and the shoulder far forward (practice). Plan the exit: a step aside or a pivot, hands up. The handbook shows how to change distance after an attack, for instance with side and backward steps [1]. Milestone: overhand, step aside, stance – as one movement.
The overhand commits body and attention forward. If you miss, you often stand with a turned back and an open side, and that is a moment for the counter (practice). That is why the exit matters.
The hand remains the risk point: in a British national squad there were 302 hand injuries per 1000 hours of competition [6]. Hand wraps, suitable gloves, pads or bag instead of a head.
For sparring: boxing is a sport with head impacts. A meta-analysis of 35 studies found a clearly higher concussion risk in boxing than in other combat sports (risk ratio 0.253 versus 0.065) [7]. Sparring only under a coach's supervision, with a suitable partner, headguard and 16-ounce gloves [1]. Warning signs like nausea, confusion or dizziness after a hit require stopping at once and medical help [1].
This guide explains and motivates; it does not replace supervised training.
Let the overhand run only after a fake, never as an opener. The handbook describes feints as preparation of the attack: they come before the punch, are very quick, and the following action must also be quick [1]. A small feint with the lead hand, then the arc: the feint draws the eyes, the arc comes from the side where the opponent is not looking. That is the practice idea; the overhand itself is not named in the source.
A cross that runs to the target in an arc from above instead of going straight. In the federation material read the punch is not described [1][2]; it is gym knowledge based on the cross. The technique here is practice.
Many gyms claim so; I could not confirm it with the sources read. The handbook recommends closeness, hooks and uppercuts against tall opponents [1]. As a beginner, learn those punches first when in doubt.
The cross travels on a straight path, the overhand in an arc from above. The cross is described as a straight punch in the handbook [1]. The arc costs speed and guard but offers a different angle. I found no measurement showing whether it is faster or slower; hooks take longer to land than straight punches in comparison [8].
With hand wraps, suitable gloves and landing with the knuckles instead of the side of the hand [3][1]. The hand is the most common injury site in boxing [6]. Hit pads or bag, not heads, until your coach says otherwise.
The movement, yes: shadowboxing in front of the mirror, standing bag. Timing against a moving opponent, no. Start standing, as the federation teaches [1], and only once the cross works.
Clinch in Boxing: Using Closeness Without Breaking the Holding Rules