Sometimes you can see what the author was getting at, such as the sign that warns people to "keep valuables snugly", and "beware the people press close to you designedly".
Then there are signs where they have mistranslated a crucial word.
One in a hotel lift advises people "please leave your values at the front desk".
Sometimes they have just got it the wrong way round, such as on the sign in the stairwell of a department store asking shoppers to "please bump your head carefully".
My favourites though, are those which get more surreal, like the one on the Shanghai metro from the public security bureau that reads: "If you are stolen, call the police at once."