When Neighbors Complain
Several years ago I was living in an apartment just outside of Seattle. The building was originally an army barracks and the walls were not at all sound proof. During that time a received several noise complaints due to my practice schedule. I decided I would commit at least part of my practice routine to studying the neck without strings.
I took the guitar neck off one of my electric guitars and studied patterns. I imagined the sounds it would make if it had strings on. This turned out nicely. Without the guitar body I could also take it on road trips and work on things in the passenger seat.
I began to think about taking the strings off an old inexpensive archtop I had bought when I was a teenager. So I did. The nice thing about this was I could think about percussion with both hands. This was so much fun. I worked a lot, and still do, on tapping steady eighths or other values on the neck with the fretting hand while tapping subdivisions on the body with the picking hand.
There are many other exercises available too. I would recommend you try this out if you have an extra guitar or two. Eventually, I plan to find a fretless neck to replace that first neck I took off. And the archtop will remain without strings and hardware. Have fun and let me know what you come up with.