Catch 22

Not the novel by Joseph Heller.
break glass
It says Martillo rompecristales. Romper el cristal para acceder al martillo.
Literally ‘Glass-breaking hammer. To get hammer break glass’.
The hammer is for breaking the carriage windows, and is probably behind a thin sheet of glass which can be broken easily by an elbow or shoe (I didn’t think it prudent to find out).