Police in Bognor Regis and Littlehampton have warned drivers to be vigilant after a number of vehicle break-ins across the two areas.
Cars and company vans with sign writing have been targeted while left in car parks or in the street.
The majority of items stolen have been power tools, and thefts have taken place at night and during the day.
PCSO Michelle Davies said: “There have been incidents of these being stolen whilst the driver has visited local hardware stores for only a brief amount of time.
“Please ensure you secure your vehicle and if possible remove any valuables or tools.
“Be vigilant and ring Sussex Police on 101 if you suspect suspicious activity is taking place. Contact your local officer through the Sussex Police website if you require security marking for tools or any other valuables.”