This is a truly awesome and fairly unique trail in the area that takes advantage of the features of the limestone bedrock that makes up the mountains in the area. Expect to frequently run up to horizon lines that seem to indicate a cliff and boldly go over them. You'll be on 30-40% slabs several times throughout the descent and challenged by very rugged running on sharp, bare rock the whole way down. There's some great steep dirt singletrack as well. Not for the faint of heart.
The easiest access is to take the Quaite Valley Trail
and at the junction with the Prairie View Trail
and turn left. Follow this for 460 metres or so up rooty terrain and watch for the left turn that takes you to the start of Razor's Edge.
The trail is straightforward, just follow it. I'd bring a phone, though, in case you miscalculate badly.