At one job, I had a USB device with scripts and directions on it. I stored it in a known location so any admin would be able to get to it if needed. It had directions for properly shutting down SQL Server and restarting it. Commands for restoring databases. Diagnostic commands. There was a main file that listed what every other file was and what they were used for.
That way if I was away, I could walk another person through what needed done in almost any situation. 'Run this script - okay, what's the result? Now run this one'.
I needed it since the site I worked at was a classified site and we couldn't remote in. As the only SQL Server DBA, I needed to be able to have another Admin (security/system/application) 'step in' for me when I was away. I could help them over the phone when I couldn't get into work.
Unfortunately, I created the USB drive at work and was not allowed to take it with me. At my new job, we have so many DBAs we are covered 24/7.