I have a vast collection of boss pedals, from collecting them over the years, and i was recently going through the manuals for some "suggested settings" and some of my pedals are compatible with the FS-5L or FS-5U. Before i go out and buy one i want to know what they do. The Boss website doesn't give detail.

tl dr

Whats is the boss Fs-5L/U used for?
i use a fs5u (unlatched) as an external tap tempo for my dd-20. i know that the delays with expression outs can all use them. most of the twin pedals can use them in some way. what are you looking to use one for?