If your synthetic turf is coming up against a patio or a garden element, you need to cut it up to an edge. 

• Place the turf over the edge 
• Hold the knife in one hand 
• Use the other hand to pull back the piece of the turf you need to remove to expose backing 
• Start cutting in small segments 
• Keep pulling the excess piece of turf up and back while cutting 

If the turf runs up against a wall, you need to fold the excess turf away from the wall and toward you. Then, start cutting horizontally while keeping the turf folded.  After cutting every few inches, lay the turf against the wall to check the fit.