מנעול הצירופים ליד לוח המקשים.

Because Hebrew often leaves out the verb to be in the present tense.

So:

• מנעול הצירופים ליד לוח המקשים
  means
• The combination lock is next to the keypad

Even though there is no separate word for is.

This is very common in Hebrew. In the past or future, Hebrew would normally use a form of היה:

• מנעול הצירופים היה ליד לוח המקשים = The combination lock was next to the keypad.

Because מנעול הצירופים is a construct chain (called סמיכות in Hebrew).

In a construct chain:

• the first noun usually does not take ה־
• the definiteness of the whole phrase is usually shown on the last noun

So:

• מנעול צירופים = a combination lock
• מנעול הצירופים = the combination lock

Even though מנעול itself does not have ה־, the whole phrase is definite because הצירופים is definite.

You should think of it as one noun phrase made of two nouns:

• מנעול = lock
• הצירופים = the combinations

Together, in a construct chain, they mean something like:

• lock of combinations
• more naturally: combination lock

This kind of structure is extremely common in Hebrew. Another famous example is:

• בית הספר = the school
  literally house of the book

So yes, it is two nouns grammatically, but together they function as one phrase.

Because the normal Hebrew expression for combination lock is מנעול צירופים.

Literally, צירופים means combinations or combinations/sequences. Hebrew uses the plural in this set expression, even though English usually says combination lock with singular combination.

So this is less about strict logic and more about the standard collocation in Hebrew. Learners should treat מנעול צירופים as the normal expression.

ליד means:

• next to
• beside
• by
• sometimes near

The exact English choice depends on context.

In this sentence, ליד לוח המקשים means next to the keypad or beside the keypad.

It is a very common preposition in Hebrew.

For the same reason as מנעול הצירופים: this is also a construct chain.

• לוח = board / panel
• המקשים = the keys / buttons

Together:

• לוח המקשים = the keypad / key panel

In Hebrew construct chains, the first noun usually does not take ה־, even when the whole phrase is definite.

So:

• לוח מקשים = a keypad
• לוח המקשים = the keypad

Not normally הלוח המקשים in this meaning.

It can mean either keys or buttons, depending on context.

The singular is:

• מקש = key / button

The plural is:

• מקשים = keys / buttons

So לוח המקשים is a panel with keys or buttons on it. In natural English, that is often translated as keypad.

Yes. The sentence has a very natural Hebrew order:

• מנעול הצירופים = the subject
• ליד לוח המקשים = the location

So the structure is basically:

• [subject] + [location]

This is the normal way to say The combination lock is next to the keypad.

You can sometimes change the order for emphasis, but the given order is the most straightforward and neutral one.