Treat your picture frames to a biscuit for reinforcement
Picture frames benefit greatly from reinforcement at the mitered corners. I prefer biscuits because they stay out of sight from all angles. To ensure fast and accurate placement of the biscuit slot in the mitered ends, I made a wood auxiliary fence that attaches to the joiner's fence.
An indexing pin added to the auxiliary fence ensures centered slot placement for right- or left-hand cuts. Center the pin on the length of the auxiliary fence; its placement on the width of the auxiliary fence depends on the width of your workpiece.
—Vern Hellewell, Moses Lake, Wash.