La montura transparente no está rayada.

Because montura is a feminine noun in Spanish, so it takes the feminine article la.

That also affects other words that describe it:

• la montura
• rayada (not rayado)

In Spanish, nouns have grammatical gender, and adjectives usually agree with the noun.

Because rayada agrees with montura, which is feminine singular.

Agreement here is:

• montura = feminine singular
• rayada = feminine singular adjective/past participle

Compare:

• el cristal está rayado = the lens/glass is scratched
• la montura está rayada = the frame is scratched

Some Spanish adjectives have the same form for masculine and feminine. Transparente is one of them.

So you get:

• el marco transparente
• la montura transparente

But it still changes for number:

• la montura transparente
• las monturas transparentes

Spanish usually uses estar for a state or condition, and ser for a more essential characteristic.

Here, rayada means scratched, which is treated as a condition or result, so Spanish uses estar:

• La montura está rayada = The frame is scratched.

Using ser rayada would sound wrong here in normal Spanish.

In standard Spanish, no normally goes directly before the conjugated verb.

So:

• no está = is not

That is the normal pattern:

• No es caro.
• No tengo tiempo.
• No está rayada.

Here, montura most naturally means the frame, especially the frame of glasses.

Montura can have other meanings in other contexts, such as:

• a mount
• a setting
• a saddle

But in a sentence like this, la montura transparente strongly suggests something like the transparent glasses frame.

In Spanish, adjectives often come after the noun, especially when they describe a basic, objective quality.

So:

• montura transparente = transparent frame

That is the most neutral order.
You may sometimes see adjectives before the noun in Spanish, but that often changes the tone or emphasis.

Grammatically, it is possible, but it sounds much less natural in everyday Spanish.

For a simple descriptive sentence, Spanish strongly prefers:

• La montura transparente no está rayada.

Putting transparente before the noun sounds more literary, marked, or stylistically special.

Yes, rayado/rayada is a very common way to say scratched.

It comes from raya = line/mark, so rayado suggests something marked with lines or scratches.

Depending on context, Spanish can also use words like:

• arañado/arañada = scratched, scraped
• rascado/rascada = scraped

But for an object like a frame, rayada is very natural.

Yes. In other contexts, rayado/rayada can have other meanings.

For example, in colloquial Spanish:

• estar rayado can sometimes mean being obsessed, bothered, or mentally stuck on something

But in this sentence, because the subject is la montura, the meaning is clearly physically scratched.

Because la means the, and the sentence is talking about a specific frame, not just any frame.

Compare:

• La montura transparente no está rayada. = The transparent frame is not scratched.
• Una montura transparente no está rayada. = A transparent frame is not scratched.

Both are grammatical, but they mean different things.

You would make the noun, article, verb, and adjective plural where needed:

• Las monturas transparentes no están rayadas.

Breakdown:

• la → las
• montura → monturas
• transparente → transparentes
• está → están
• rayada → rayadas

In Spain, it is usually pronounced approximately like:

• ra-YA-da

A rough guide:

• ra as in rah
• ya as in yah
• da as in dah

In most of Spain, y and ll are pronounced similarly, so rayada sounds with a y sound in the middle.