The Klip Halo bolts directly onto the BBC micro:bit using five supplied screws which are secure and robust. The supplied mounting bar is used to fix the microbit to Klip Halo and already contains the required nuts as well as additional solder pads (PO, P1, P2, 3V & GND) should you require them. There are multiple power and ground pads so that the same pads don't have to be used for every part of your project, which is a handy feature if you are using Crocodile clips. Power is supplied to the board and the microbit via the rear mounted jst connector.
When a micro:bit is connected to the Klip Halo, power can be supplied in multiple ways. These are via the USB connector on the micro:bit, the JST connector on the micro:bit or Klip Halo, or using the power rings on the Klip Halo. Depending on which option is used effects the maximum and minimum voltage that can be used and the amount of current that can be drawn from the rings on the Klip Halo. For more details and powering safety information, see the power information and safety datsheet for more information. Supply voltage should be between 1.95V and 3.6V with 3V being the recommended voltage.

Datasheet
Power Information And Safety Datasheet