Czenglish: Here is the form. Please fill in the backside as well.
English: Backside means bum.
Czenglish: I mean the other side… The back!
As with a lot of Czenglish the meaning here is so obvious that you are unlikely to be corrected. You may get a raised eyebrow and a smile though! To avoid any embarrassment it is better to say ‘the other side’ or ‘the back’.