What does 'lining' a painting mean?

Lining is a major treatment in paintings conservation, and should only be used when absolutely necessary

What Is an Implied Line in Drawing?

Christies - What to look for on the back of a painting: an expert

Line art - Wikipedia

Contour Line - Mrs. Cook's Art Class

Lining paintings - Procedures and techniques - ARTEnet

Lining the Painting

Finishing the relining Art restoration of Artemisia

Restructure: Unpacking the Treatments of Two Lined Portraits

What does 'lining' a painting mean?

Lining the Painting