Final answer:
A mechanic's lien or a contractor's lien is filed by George against Martha's property to secure payment for the work done.
Step-by-step explanation:
When George files for a lien against Martha's property to secure payment for the work he did, this encumbrance is called a mechanic's lien or a contractor's lien. A mechanic's lien is a legal claim against a property filed by someone who has provided labor or materials for improvement to that property but was not compensated for the work. It allows the person to seek payment from the property owner by forcing a sale of the property.