Police in Gwynedd say they have received several reports of cold-callers in the region in recent days.
Officers are urging people not to engage with the door knockers or say ‘no thank you’ and to keep their doors locked.
North Wales Police Gwynedd South said in a social media post: "We’ve received several cold-caller reports in the area in recent days.
“These reports have generally related to individuals knocking on at properties and offering household goods for sale.
“Our advice is to always politely say 'no, thank you' and close the door to this kind of visitor.
“A general rule of thumb to follow is always keep all your doors locked even if you are in the house.”