#Person1#: You mustn't touch the wet paint, Bill.
#Person2#: I'm sorry. I won't do it again.
#Person1#: Try to be more careful in future.
#Person2#: I shall. I wasn't as careless as John Sampson. He walked across that wet cement over there.
#Person1#: The workmen oughtn't to leave it without a notice.
#Person2#: The headmaster asked them not to do so.
#Person1#: Then why isn't there a notice?
#Person2#: They went to their stores to get one. Here they come with it now!
#Person1#: But look at them! They've forgotten about the wet cement and they're walking across it to put up the notice!
The workmen are walking across the wet cement to put up the notice.