Plank Mounting
Using the spacer and rimless adapter
The flat bar with two holes is used to create a bit more distance between the top and bottom halves of the Plank mount when used on tanks with thick plastic rims or Eurobracing. This allows the mounting platform's edge to grab under the lip of the plastic frame or Eurobrace. Every Plank comes with one of these; you can stack them if the trim or Eurobrace is extra thick.
Rimless spacer adapter
The angled bar is used to “fill in” the gap in the lower half of the mount which is typically used to grab the plastic rim of many aquariums. When used on a (t)rimless tank, this flat surface to clamp against creates a more secure hold for the mount.
Integrating the Plank with Screen Tops
The best way to use a screen top with the Plank is to create a "cutout" area, typically in a corner, for the mounting platform. This allows you to easily lift or remove the screen top without needing to move the Plank. Nearly every screen top style available (Red Sea, BRS, etc) has a kit that includes two extra right angle corners and a short length of the frame material. Here is an example of using a corner kit (this one is from BRS) to create a custom Plank integrated screen top:
