For added security tie a safety knot by passing the finishing loop through the carabiner. Alternatively, clip a carabiner into the finishing loop and then clip this to something else (harness etc.) - ...

Make sure that there is at least 3 inches of tail leaving the knot. Tie off the extra tail of rope to the live end of the rope using several overhand knots or a double fisherman's knot. Clip a locking ...

According to "Climbing: Knots" by Nate Fitch and Ron Funderburke, to tie a knot, there must be a tail ... it must be looped ...