Abstract: An aluminum picture frame conventionally comprises: four perimetric frame sections of U-shape in cross-section, each section having a perimetric wall, a ribbed front face flange and a ribbed rear face flange which should be narrower than the front face flange, each ribbed face flange being mitered at its opposite ends, the adjacent mitered ends of these sections being rigidly joined to form an integrated open-ended frame. At least one mat-retaining spring is used in each of two or more opposed frame sections to retain a mat extending across the inner side of the front face opening of the frame. The preferred form of each retainer comprises: a spring wire open-looped or corrugated at intervals along its length to form a narrow strip of suitable length, which is bent to a concavo-convex shape to provide it with a resilient concavo-convex undulation.