RHT is short for Right Hand Traffic and LHT is short for Left Hand Traffic.RHT is the same as LHD (Left-hand drive) and LHT = RHD (right-hand drive)In most countries, you have to drive on the right side of the road and therefore you need a RHT cut-off shield in your projector. There are a few countries that drive on the left side of the road and therefore need an LHT cut-off shield in the projector. For example, the United Kingdom, Australia, and Japan.It is of great importance that you use the correct cut-off shield in your projector when driving on the public road. Using the incorrect cut-off shield will blind oncoming traffic and you will cause dangerous situations. Here you can see an illustration of an RHT (LHD) cut-off light pattern. As you can see, the cut-off shield prevents the light of your headlights to blind oncoming traffic on the other (left) side of the road, the right side is higher.When using an LHT (RHD) cut-off shield in the projector, the pattern on the left side is higher and the right side (oncoming traffic) is lower. This is an illustration of the light pattern that you will see in front of you when driving a car for Left-hand traffic.