Remove the 4xH5 22mm Screws from the end.

If the shredder is siezed, spray in the marked locations with some penetrating spray and give it a few minutes to soak in.

Take a big hammer and tap on alternating sides to try get the end cap off. The amount of force you need will vary from "just a light tap" to "am I going to break this?" depending on how rusted in it is.

Once you get the end off you can take out the adjustment piece - note there's a plastic spacer and a nut that goes onto the red adjustment knob, put these aside so you don't lose them!