This filter provides two "notches" that can be adjusted to blank out either a single UHF channel or two separate UHF channels. It is most effective if both adjusters are turned to blank out a single channel.
To blank out a channel, tune your receiver then turn the first adjuster until the signal is minimum. Then turn the second adjuster to further reduce the unwanted signal. (The adjustment is most easily achieved by using a spectrum analyser but it is possible to achieve a good approximation by trial and error.)