Passive A/B switch box

Hi guys, I want to build a simple passive A/B switch to easily try out/swap 2 different amps, using the same guitar or turning it around and be able to A/B 2 guitars with the same amp.  

I was looking for schematics online and came across this: www.fulltone.com/sites/default/files/manuals/fultone-a-b-switcher.pdf

It seems perfect for my needs, right? 

And, the last question, all grounds (sleeves) go together, right?

Thanks in advance, my electronics knowledge doesn't go too deep at all.