>>1900054you loosen the rear bolt and then position it with the first nut infront of the fork crown. Usually you need this tool to do that, but sometimes a regular spanner or cone spanner will fit.
You can actually just hold the whole brake caliper with your hand to position it, instead of the offset wrench, and then tighten it, it just takes a bit of trial and error.
One thing to be careful of is that if the mounting bolt thread is stiff/ gunked up, and you torque down hard on it, you can end up loosening the whole brake assembly. So if it's stiff to tighten, you should clean and grease that thread.
Also if they're modern brakes, dual pivot calipers have a little allen screw on the top for fine tuning the centering adjustment.
