The B6405 is a rural link road in north Roxburghshire. It was originally unclassified but gained its number in the late 1920s.
The road starts on the A698 in the centre of Denholm and skirts the green before zigzagging out of town and over the River Teviot. The road now runs towards the Minto Hills, briefly visible ahead, and narrows as it passes to the west of the village of that name. After bending round to the left and going under a bridge carrying a dismantled railway line the road ends at a T-junction on the B6359.