Çatı kancası montaj rayının altında.

In Turkish, the verb to be is often omitted in the present tense when the sentence is just identifying or locating something.

So this sentence is literally structured like:

• Çatı kancası = the roof hook
• montaj rayının altında = under the mounting rail

The full idea is The roof hook is under the mounting rail, but Turkish normally does not need a separate word for is here.

If you wanted to make it past tense, then Turkish would add a form of to be, for example:

• Çatı kancası montaj rayının altındaydı. = The roof hook was under the mounting rail.

This is a very common Turkish noun pattern called an indefinite noun compound.

• çatı = roof
• kanca = hook
• çatı kancası = roof hook

In this structure, the second noun usually takes a 3rd person possessive ending:

• kanca → kancası

So even though English just says roof hook, Turkish often builds this kind of expression as something like roof-its-hook.

Other examples:

• araba kapısı = car door
• ev çatısı = house roof
• güneş paneli = solar panel

So çatı kancası is the normal way to say roof hook.

Because there are actually two layers of grammar here.

First:

• montaj rayı = mounting rail

This is another noun compound:

• montaj = mounting / assembly
• ray = rail
• rayı = rail + compound ending

Then that whole phrase is put into the genitive case because it is followed by altında:

• montaj rayı → montaj rayının

So the parts are:

• ray-ı = the compound form in montaj rayı
• rayı-nın = of the mounting rail

This is completely normal in Turkish.

Because Turkish usually expresses under X, over X, inside X, in front of X, and similar ideas with a possessed location noun.

The pattern is:

• X-in altında = under X
• X-in üstünde = on / above X
• X-in içinde = inside X
• X-in önünde = in front of X

So:

• montaj rayının altında = under the mounting rail

Here:

• montaj rayının = of the mounting rail
• altında = at its underside / under it

This is a very standard Turkish structure, so learners should get used to seeing genitive + altında/üstünde/içinde/önünde/arkasında.

Altında can be broken down like this:

• alt = lower part / underside / bottom
• -ı = its
• -nda = in/on/at

So literally it is something like:

• at its underside
• or on its lower side

That is why X-in altında means under X.

A few related forms:

• altında = under it
• üstünde = on it / above it
• içinde = inside it
• yanında = next to it

These forms often behave like postpositions in English translation, but grammatically they are built from nouns plus suffixes.

Because they are doing two different jobs.

1. kancası
   This is part of the compound noun çatı kancası = roof hook.
   The possessive-looking ending is just how Turkish commonly forms this kind of compound.

2. altında
   This is part of the location expression montaj rayının altında = under the mounting rail.
   Here the possessive ending belongs to alt and helps form the expression under it / at its underside.

So although both contain endings that look similar, they are not the same kind of structure in practice:

• çatı kancası = a lexical noun phrase
• montaj rayının altında = a location phrase

Not completely. Turkish word order is flexible, but the version here is very natural and neutral.

• Çatı kancası montaj rayının altında.
  = The roof hook is under the mounting rail.

You could also say:

• Montaj rayının altında çatı kancası var.
  = There is a roof hook under the mounting rail.

Or, with emphasis on location:

• Çatı kancası, montaj rayının altında.

Turkish often puts the most important or new information near the end, but simple subject + location order is very common in basic descriptive sentences.

Turkish does not have articles like English a/an and the.

So a phrase like:

• çatı kancası

can mean:

• a roof hook
• the roof hook

depending on context.

Likewise:

• montaj rayı
• montaj rayının altında

do not need an article word.

Turkish usually leaves definiteness to context, word order, or other markers if needed.

A rough pronunciation guide is:

• çatı ≈ CHA-tuh
• kancası ≈ KAN-ja-suh
• montaj ≈ mon-TAZH
• rayının ≈ ra-yuh-nuhn
• altında ≈ al-TUHN-da

A few useful sound notes:

• ç = ch as in chair
• c = j as in jam
• ı = a vowel English does not really have; it is like a short, relaxed uh said without rounding the lips

So kancası is not kan-ca-see; it is closer to kan-ja-suh.

Not very naturally. A word-for-word version would come out something like:

• roof hook mounting rail-of under-its

That sounds strange in English because Turkish builds relationships with suffixes and possessed location words rather than separate prepositions in the same way English does.

The natural English translation is:

• The roof hook is under the mounting rail.

So it is better to understand the Turkish structure as:

• thing being located + reference object in genitive + location word

rather than trying to match each Turkish word directly to one English word.

A very useful pattern is:

• [Noun] [another noun]-ın/-in/-un/-ün altında/üstünde/içinde/önünde/arkasında

Examples:

• Kablo panelin arkasında.
  = The cable is behind the panel.

• Vida profilin içinde.
  = The screw is inside the profile.

• Etiket kutunun üstünde.
  = The label is on the box.

And also learn the noun-compound pattern:

• çatı kancası = roof hook
• montaj rayı = mounting rail
• güneş paneli = solar panel

This one sentence contains two very common Turkish structures:

1. noun compounds
2. genitive + location expression