A trellis is a frame supporting open latticework, used for training vines and other creeping plants.
An arbor or arch made with a trellis structure is likewise referred to as a trellis.
In the transitional verb sense, to trellis is to train a plant on a trellis.
To make something in the form of a trellis also is to trellis, again using the word as a transitional verb.
This sentence no verb.