Learn the topout in bouldering: mantle onto the ledge, bring your weight over the foot and downclimb safely. With milestones and the safety rules that matter.
A topout means: at the end of the boulder you do not just reach the top hold, you climb over the edge onto the block or the wall, stand up and downclimb safely [1]. The honest answer to "Isn't that just the last move?": no. The topout is the moment when most people have already given up their concentration. You need a movement the DAV describes as a mantle: hands and feet are almost side by side, you support yourself and push upward [1].
Biomechanically it is a shift of weight: you bring your center of mass over the foothold and lower the heel instead of pulling up on your arm [2]. Important up front: only top out where it is expressly allowed on that boulder [1].
Expect to learn the mantle on a low ledge first before using it at height, and expect that to take several sessions (an experience value, not a measurement).
Entry criteria (practice standard):
Ask the gym staff or read the gym rules. The DAV rule: you climb only up to the top holds, not further, unless the topout is allowed [1]. Find the way down before you start.
Milestone: You can describe the descent without looking.
Stand in front of a ledge at hip height, put both palms flat on it and push yourself up until your hips are above the ledge. That is the mantle [1].
Milestone: Five clean mantles in a row without sliding over the ledge on your belly.
Place the foot on a hold near the edge. Do not yank it up, guide it, because a high step is one of the four mechanisms behind acute knee injuries in a case series (20.8% of 77 injuries) [3].
Milestone: You place the foot three times while looking at the hold, without the knee collapsing inward.
Shift the weight onto the high foot and lower the heel until your center of mass is over the foothold [2]. The leg does the standing up, not the arm.
Milestone: You stand up from the squat without pulling yourself up with your hands.
Only stand when you are stable. Then look for the way down via the downclimb holds [1]. If you jump, do it with a clear landing area and from as low a height as possible.
Milestone: You top out an easy boulder and downclimb the designated way.
The risk is not in the mantle but in the height. A fall from the top can end badly: in a survey of 245 injured climbers, the fall started in the upper wall section in 47% and in the middle in 32%, and 74% landed on their feet first [4]. In a hospital series the mean fall height was 2.9 meters, ankle fractures made up 40% of the diagnoses, and 24% of the patients were operated on [5]. Injuries of the lower extremity are more often severe and more often caused by falls and jumping off than injuries elsewhere [6]. The DAV puts it plainly: the mat is harder than you think, and downclimbing is always safer than jumping [1]. This guide explains and motivates but does not replace supervised training. Have a coach show you falling technique and mat rules.
Do a rehearsal topout at jump-down height: pick a low block, practise mantle, foot and standing up at knee height and deliberately jump off again. That way you train the movement and the landing without a mistake becoming expensive. This is practical experience and not proven.
In a topout you climb from the last hold further onto the wall or the block, stand up and downclimb at the top [1]. It is not standard in every gym: only top out where it is allowed.
You need a mantle: hands flat on the ledge, push, then foot up and bring your weight over the foothold [1][2]. After that you stand up through the leg and downclimb via the downclimb holds.
It has its own risk: height. In a survey of injured climbers almost every second fall started in the upper wall area [4], and the mean fall height in a hospital series was 2.9 meters [5]. So: only where allowed, know the descent, and when in doubt downclimb.
Downclimb as far as you can. The DAV is clear: downclimbing is always safer than jumping down, because the mat is harder than you think [1]. Jump only from low height and only if the landing area is clear.
Layback: Pull on the Edge, Push With the Feet