Can you really practice chords without your guitar?

When you don't have your guitar with you but still want to practice somehow, no problem! Use your forearm like a fretboard and imagine the notes in your mind. Whether you're memorizing the notes on the fretboard or learning chords, scales, arpeggios, etc, try envisioning the fretboard in your head and use your forearm to find your frets & fingerings. It will help your playing and your knowledge of the fretboard. Improve your technique by building up your finger independence & coordination by doing hand exercises like those shown in this video. Being able to see the guitar in your mind will help so much in becoming more familiar with it, the notes and shapes, and helps you memorize what you're learning.