The core grammatical concept in Unit 5.4 is the "designation of locations." Since the people being discussed are not physically present, the signer must establish a point in space to represent them.
Here are the primary signs introduced in this unit: signing naturally 5.4
Whether you love them or "detest" them, these are the signs you'll need to master for this unit: The core grammatical concept in Unit 5
Describing cars (e.g., green, medium-sized, 4-seater vs. blue, small 2-seater). 4-seater vs. blue