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 bike up to horizon lines that seem to indicate a cliff and boldly ride off them. You'll be on 30-40% slabs several times throughout the descent and challenged by very technical riding on sharp, bare rock the whole way down. There's some great steep dirt singletrack as well. Not for the faint of heart and, although many don't bother, elbow and knee guards are a great idea at a minimum (having lost a pound of flesh to this route myself, I wear my armour jacket.)
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. For added excitement, go with someone who has ridden it before and follow closely - when they ride off seeming cliff edges, follow blindly. Huge adrenaline hits will be yours. If you're solo on your first ride, you'll likely want to peek before you leap. Virtually everything is rideable by a good rider who is on their toes. I'd bring a phone, though, in case you miscalculate badly.