These are the probable methods competitors may use to remove weed.
The rules permit a crew to leave the boat to swim, but he must be back on board before the boat “continues in the race”.
This implies the boat must stop if a crew is swimming to remove weed.
Crew leaning (or even being lowered) over the side to check for weed or to use a weed stick breaks no rule. Even when the boat has lifelines this is permissible if the action can be considered “brief and to perform a necessary task”.
However using a halyard, harness, hobbles etc. to help project or lower a crew member overboard would break rule 49.1 as this would be considered ‘a device designed to position their bodies overboard’.
No rules prohibit the system of dropping a sheet over the bow and holding the ends while walking it back (or letting the boat sail over it) then pulling one end to wipe it across the front of the keel.
A ‘weed stick’ manipulated from the deck breaks no rule (but don’t use it like an oar).
Some boats have had cutters built into the front of the keel. These or similar implements constructed as part of the boat are legal unless they contravene some class rule. (Examples of class problems could be a one-design class requiring the keel to fit a standard template, or a cutter projecting from the hull when the class has specific “appendage” restrictions.)