No ,there is no screw down piece for the top of the Dot RBA except for the chimney that fits over the build , any 510 drip tip should just fit in the opening of the top of the mod once the RBA is installed not a separate piece that you have to screw down - the one metal piece in my picture goes onto the bottom of the RBA that goes in the mod, it is the air flow adjuster too as well as the contact for the mod,the other metal piece is to build your RBA and be able to connect it to a separate mod or Ohm reader to make sure your coil is the right ohms since you can't do that in the Dot AIO .
The Billet Box needs a metal screw piece to contact the RBA and the Drip Tip, not the Dotmod RBA
I usually look up tutorials on You Tube, much easier to see than explain in writing, I hopes this tutorial helps you understand the Dotmod RBA better.