Helix Weir Block Plates can be used to isolate the Helix pond skimmer from the rest of the pond. Which option you need will depend on whether you want a permanent or removable block plate.
The Removable Weir Block Plate allows you to temporarily block the mouth of the skimmer so that the skimmer can be emptied without lowering the pond's water level. The block plate has no gaskets, so it won't keep out all water indefinitely, but it is a quick and easy solution for working inside the skimmer without draining the pond. Keep a Removable Block Plate on hand for those situations where it makes your work that much easier!
The Permanent Weir Block Plate is meant to be installed directly onto a Helix skimmer body with lap sealant to create a watertight seal. This allows you to use a skimmer body for creative purposes like a remote holding tank.