They were repairing the roof when the owner arrived to see how things were progressing.
The phrasal verb "was repairing" could be used as follows: I was repairing a faucet when the doorbell rang, interrupting my work as I went to answer the door.
The shed was so dilapidated that it wasn't worth repairing.
The shed was so dilapidated that it wasnt't worth repairing .
Protein
Multimeter for starters
i do not know how to use embalming in a sentence. (there is the sentence)
A cell uses Proteins for repairing and building up muscles injuries.
Metric sized wrenches and sockets
You use a scan tool after repairing the failure.
So- you are asking when to use 'when' in a sentence. When you are asking how to use when in a question, you are already using when in a sentence, because a question actually is a sentence. I like to use when in a sentence whenever I like.
How do use evidenced in a sentence
can i use polymer in a sentence