Chop off your tail
Nqumla Umsiila Wakho : chop off your tail
Nqumla: chop or cut through
This is a idiom meaning effectively 'close the door behind you'.
The basic way would be to say 'vala ucango' : close the door
or if you wanted to be more polite: 'Khawuvale ucango' : please close the door
You can use 'Khawu' on the start of a verb to act as saying please, and then just change the ending 'a' to an 'e' (basically to show that it is a directive).
Khawuthule: please (be) quiet
Khawuphinde: please repeat
Khawucacise: please explain
Also, as well as Nqumla (chop), there are a few alternatives for cutting:
ukusika: to cut
ukusarha: to saw
ukucheba: to cut/shave/trim (hair or grass..) - ucheba iinwele: you cut hair