把（BA） as a verb means ‘to grasp’ and its grammatical function as a coverb derives from this meaning. The subject of the sentence essentially ‘takes’ the object, physically or metaphorically, and does something to it. In grammatical terms the effect of this is to move the object to the front of the verb. This leaves the space behind the verb to be occupied by the results of the action of the verb on the object. These results are expressed in the form of complements. For example,
他把杯子洗干净了。
Tā bǎ bēi zǐ xǐ gān jìng le 。
He washed the cup(s) (so that the cup(s) is/are clean).
or:
他把杯子洗得干干净净（的）。
Tā bǎ bēi zǐ xǐ dé gān gān jìng jìng （de ）。
He washed the cup(s) thoroughly/He gave the cup(s) a good wash (so
that the cup(s) is/are completely clean).
[1] Yip, P. C., Rimmington, D., Xiaoming, Z., & Henson, R. (2009). Basic Chinese: a grammar and workbook. Taylor & Francis.
