Signal and phone cables, electric wires, road signs. They're are all sort after as the price of scrap metal continues to rise.
All over Britain, drain covers are being stolen, putting drivers and pedestrians at risk of serous injury and death.
Today Birmingham City Council is to demonstrate its latest weapon.
It's called DNA Grease.
Gully grids are to be coated in the stuff - indelibly marking anyone who touches them.
The hope is it will make it easier for the police to trace thieves, and to link them to a specific metal crime via a unique DNA code.
Like "Smart Water" - which has been around for a number of years - it will show up clearly under ultra-violet light.
The grease has been used in Derbyshire following a series of lead thefts.
And as far back as 2008, it was used by under-cover police officers in decoy vehicles to target car thieves.
There's a second possible solution to the problem - grids made of a composite material that has no re-sale value.
And this too is to be trialled by the city council and its partner, Amey.
Only a few days ago drain covers were taken from four roads in the Edgbaston area of Birmingham - leaving holes next to pavements large enough for an adult to fall through.
At a demonstration in Sutton Coldfield this afternoon, council officials and police will explain more about how DNA Grease works.
Thieves will be warned it's in use by signs fixed to lamp posts.