Le grimpeur garde une main sur la prise.

Le grimpeur means the climber.

French often uses le / la / les in two common ways:

• for a specific person or thing already understood from context
• for a general statement about a type of person or thing

So in a caption or exercise sentence, Le grimpeur can simply mean the climber you are looking at.

If you said Un grimpeur, that would mean a climber, introducing him less specifically.

Grimpeur means climber.

It comes from the verb grimper, meaning to climb.

The feminine form is grimpeuse:

• Le grimpeur = the male climber
• La grimpeuse = the female climber

In real usage, especially in climbing contexts, you may also hear other words depending on the sport, but grimpeur / grimpeuse is a very normal word.

Garde is the 3rd person singular present tense of garder.

So:

• je garde = I keep
• tu gardes = you keep
• il / elle garde = he / she keeps

Here, the subject is Le grimpeur, which is singular, so the verb is garde.

In this sentence, garder means to keep or to maintain:

• Le grimpeur garde une main sur la prise.
  = The climber keeps one hand on the hold.

No. That is a very common confusion.

Garder can mean:

• to keep
• to leave
• to look after
• sometimes to guard

In this sentence, it clearly means to keep or to maintain a position, not to guard.

So here, garde means something like:

• keeps
• keeps in place
• maintains

This is a very good question, because French handles body parts differently from English.

Why une main?

Une main means one hand.
The sentence is emphasizing that the climber keeps one hand on the hold.

That makes sense because a climber has two hands, and the sentence is focusing on just one of them.

Why not sa main?

Sa main means his hand. French often avoids possessives with body parts when ownership is obvious, unless the speaker wants to stress possession.

So:

• une main = one hand
• sa main = his hand

Here, une main sounds more natural if the idea is one of his hands.

Why not la main?

La main would mean the hand, but that is less natural here unless the context already makes a very specific hand clear.

So une main is used because the sentence is really about one hand being kept on the hold.

Sur means on.

So:

• sur la prise = on the hold

This is the normal preposition when something is physically resting or staying in contact with a surface or object.

In climbing, if a hand is placed on a hold, sur is very natural.

English and French prepositions do not always match perfectly, but here they do:

• on the hold = sur la prise

In everyday French, prise can have several meanings depending on context.

But in climbing, une prise means a hold.

So:

• la prise = the hold

This is the object the climber grabs or places a hand on.

That is why the full sentence means the climber keeps one hand on the climbing hold.

French usually needs an article before a noun.

So French says:

• la prise = the hold
• une prise = a hold

Unlike English, where you can sometimes omit articles in short labels or notes, standard French normally includes them.

Here la prise refers to a specific hold understood from the situation.

Yes.

French present tense often covers both:

• a general/habitual action
• an action happening right now

So Le grimpeur garde une main sur la prise can mean:

• the climber keeps one hand on the hold
• the climber is keeping one hand on the hold

French does not need a separate form like English is keeping in order to express an action in progress.

A careful pronunciation is approximately:

luh gran-pur gard eun men sur la preez

A more accurate IPA version is:

/lə ɡʁɛ̃.pœʁ ɡaʁd yn mɛ̃ syʁ la pʁiz/

A few useful notes:

• grimpeur ends with a French -eur sound
• une is pronounced yn
• main has a nasal vowel, so the n is not fully pronounced
• prise sounds like preez

Yes, it could be correct, but it means something slightly different in emphasis.

• une main = one hand
• sa main = his hand

So:

• Le grimpeur garde une main sur la prise.
  focuses on one of his hands

• Le grimpeur garde sa main sur la prise.
  focuses more on his hand as belonging to him

In many contexts, une main sounds more natural if the point is that one hand remains on the hold.