Landscape contractors and others who own small work trailers are being advised that they may be targeted by thieves, according to the Jacksonville, Florida, Sheriff’s Office. Unlocked trailers are being stolen in seconds by thieves who drive up, hook them up and leave.

This year, police said 73 of the open-style trailers have been stolen from across the city. Just in the month of April, 21 have been reported stolen. Owners of the trailers are warned that they need to safeguard their property by marking them and locking them.

Trailers do not have vehicle identification numbers, so they are difficult to track. The Sheriff’s Office advises owners to mark them with identifiers such as phone number, date of birth or some other distinguishing characteristic. Place the markings in several locations, and photograph the trailer.