The B664 is a cross-country route in three East Midland counties. Originally unclassified, the road dates to around 1935.
The road starts on the A427 just to the east of the A6Market Harborough bypass and heads northeastwards on a similar course to the River Welland. The road follows a straighter course as it crosses a ridge and goes through Sutton Bassett and Weston by Welland before it descends back into the valley and crosses the river, finally leaving it behind. The road continues in the same direction to go through Medbourne and then goes over the top of a hill. There's a crossroads by the trig point.
The road descends, with Eyebrook Reservoir just visible over to the right. However, on reaching the bottom of the valley we bear sharply left to go through Stockerston before a sharp right-hand bend takes us over a narrow humpbacked bridge over the Eye Brook. The road climbs steeply out of the valley via a couple of doglegs on the King's Hill and then descends gently into Uppingham. The road originally ran along High Street West but this narrow road is now one-way westbound and so the road bears left around a short one-way loop to TOTSO right into North Street West (the pre-bypass line of the A47). The road ends at traffic lights on the A6003.