Maybe a bit stupid question, but
Sometimes (rarely but it happens) I need to move a server in a rack 1-2U up or down. What do you think, which of the ways is the most correct and useful and why?
remove a server from the rails, detach a rails, attach them back to the new place, put a server back on the rails
carefully, hole by hole (or by 2-3 in one step if possible) move a rails together with a server
do everything in some other way (explain)
Please do not write "you must plan a rack before assembling" etc. This is good idea to plan everything but unfortunately the real life is not so ideal :)