Крепёж и упаковочный скотч лежат в коробке.

Because the subject is made of two nouns joined by и:

• крепёж
• упаковочный скотч

Together they mean X and Y, so Russian normally uses a plural verb:

• Крепёж лежит в коробке.
• Скотч лежит в коробке.
• Крепёж и скотч лежат в коробке.

So лежат agrees with the whole combined subject, not with each noun separately.

Russian often uses verbs that describe the physical position of things.

• лежать / лежат = to be lying
• стоять / стоят = to be standing
• висеть / висят = to be hanging

For loose objects such as fasteners and tape in a box, лежать sounds natural. Russian prefers this kind of positional verb where English often just says is/are.

A more neutral alternative would be:

• Крепёж и упаковочный скотч находятся в коробке.

But that sounds more formal and less natural in everyday speech.

Because this sentence describes location, not movement.

After в:

• в + Prepositional = in / inside somewhere
  
  • в коробке = in the box
• в + Accusative = into somewhere
  
  • в коробку = into the box

So:

• Крепёж лежат в коробке would be wrong because the case is wrong for location.
• Положи крепёж в коробку = Put the fasteners into the box.

Крепёж is a collective/mass noun meaning things like:

• fasteners
• fixings
• mounting hardware
• hardware for fastening

Grammatically, it is usually treated as singular masculine, even though in English it is often translated with a plural word.

So by itself you would normally say:

• Крепёж лежит в коробке.

Here the verb becomes plural only because крепёж is joined with another noun: крепёж и упаковочный скотч.

Упаковочный means packing or packaging-related. It is an adjective formed from упаковка (packing, packaging).

So:

• упаковочный скотч = packing tape / packaging tape

It is an adjective because Russian often expresses this idea with an adjective modifying the noun:

• упаковочный = masculine singular nominative
• скотч = masculine singular nominative

The adjective matches the noun in gender, number, and case.

In Russian, скотч commonly means adhesive tape, especially the kind used for sealing packages. The word comes from the brand name Scotch.

So скотч in everyday Russian can mean tape in general, but adding упаковочный makes the meaning specific:

• упаковочный скотч = packing tape

Without that adjective, скотч could still often be understood as tape, but the phrase here is clearer.

Here are the main nouns:

• крепёж — masculine
• скотч — masculine
• коробка — feminine

That is why:

• упаковочный is masculine singular, matching скотч
• в коробке uses the feminine noun коробка in the prepositional singular
• лежат is plural because the subject is plural as a whole

Yes. Russian word order is flexible, and the meaning usually stays the same because the forms of the words show their roles.

For example:

• Крепёж и упаковочный скотч лежат в коробке.
  Neutral statement.

• В коробке лежат крепёж и упаковочный скотч.
  More focus on where they are.

Both are natural. The original version is a straightforward, neutral order.

Крепёж is pronounced with stress on the last syllable: крепЁж.

The letter ё always indicates a stressed yo sound. In normal printed Russian, people often write е instead of ё, so you may see:

• крепеж

But the correct pronunciation is still крепёж if that word is intended.

For learners, ё is very helpful because it shows both the sound and the stress.

Because Russian has no articles.

English says:

• the box
• a box

Russian simply says:

• коробка
• в коробке

Whether it means a box, the box, or sometimes just box depends on context. Russian speakers do not need an article to make the sentence grammatical.

Not always. A literal translation can help you understand the grammar, but in natural English you often just say are:

• Книги лежат на столе.
  Literally: The books are lying on the table.
  Natural English: The books are on the table.

So in this sentence, лежат tells you how Russian describes the position of the objects, but the best English translation may simply use are depending on style.