Final answer:
When a roofer places a lien on a house to collect a debt, it is called a mechanic's lien. It is a legal claim that allows the contractor to seek payment by forcing the sale of the property if necessary.
Step-by-step explanation:
When a roofer places a lien on a house to collect a debt, it is called a mechanic's lien. A mechanic's lien is a legal claim that a contractor or construction professional, such as a roofer, can place on a property when the property owner fails to pay for the work or materials provided. This lien allows the contractor to seek payment by forcing the sale of the property if necessary.