Learn Turkish: Kutuyu tornavida ile açmışken kilidini de yağla. - Since you opened the box with a screwdriver, oil its lock too.

The suffix -ken added to the aorist (açarken) means "while in the process of opening." But adding -ken to the -miş past tense (açmışken) describes an opportunity created by an action that has already happened. It means "since you have already opened it" or "while you're at it."

Can you break down the suffixes on kilidini?

The root is kilit (lock). When we add the 3rd-person possessive suffix -i ("its"), the final t softens to d (kilidi). Then, because it is the direct object of the verb yağla, we need the accusative suffix -i, which requires the buffer consonant -n- after a possessive suffix. This gives us kilidini.

Is it possible to attach ile to the word tornavida instead of keeping it separate?

Yes, it is very common to do so. Since tornavida ends in a vowel, you would add the buffer y, making it tornavidayla. Both tornavida ile and tornavidayla are perfectly natural.

How does the word yağla work? Is it related to the word for oil?