1/2″ line comes up at the edge of the bed from a “T” fitting 4 or 5 inches below ground. A 5 inch piece of 1/2″ line comes out from the “T”, going into an elbow fitting. Out of the elbow fitting is a short piece of poly line that goes into the valve shown. The barbed valve connects into a “T” that the drip actually connects into. To make this system more flexible, a female hose coupling should have been added after the valve, that way you can swap out the drip tubing for an overhead micro sprinkler system using male threaded couplings (the kind used to cap off ends)
The advantage of the aforementioned setup with female/male couplings is the less wear and tear on the main line (pulling and moving drip tape causes tears in the poly tubing over time)
Shoshin Ecological Farming and Gardening 