The B6401 is a secondary road in east Roxburghshire. It was originally unclassified but gained its number in the late 1920s.
The road starts in the valley of the River Teviot by turning east off the A698 signed to Morebattle. The hamlet on the main road is Kalemouth and we now follow the Kale Water upstream, albeit not particularly closely: the road is considerably straighter than the river but we do have a few corners to negotiate.
Presently we reach Morebattle and run through the village along Main Street. On reentering open country we find we have left the flat land behind. We run between a couple of hills to pass the southern end of the B6436 and then skirt the edge of the valley until we cross the Kale Water. We then follow the valley of a tributary back into the hills. After going over the ridge on our right we join the valley of the Bowmont Water and follow it downstream into Town Yetholm. In the village centre we pass a turn for Kirk Yetholm, the northern end of the Pennine Way, and then continue on to a triangular junction where the road ends on the B6352. That road TOTSOs here, so continue ahead to return to the A698.