I was looking at the pictures of the newly rolled out Falcon Heavy and I noticed these odd yellow extensions on the payload faring. What are they?
They are clamps that support the fairing when the TEL is horizontal. They retract once the TEL is vertical.
Originally, the acronym TEL was used for vehicles that carried and launched ballistic missiles. Some people have started using the acronym to refer to SpaceX's launch towers (which are somewhat unusual for Western rockets - most rockets are assembled and transported vertically, this one is assembled and transported horizontally, on the TEL).
You can see below it there is a set of arms or maybe a collar that is holding the top of the stage as well. These open before launch, but also help hold the stage to the TEL as it rolls from the HIF to the launch pad. The ones higher up are just for additional support of the fairing.