A trellis is a frame made of thin strips of wood (sometimes metal or plastic) crossing over each other to leave a pattern of open squares or diamonds, put up so that climbing plants have something to hold on to as they grow. You see one fixed flat against a house wall for roses, or standing as a light fence between two gardens, or arched over a path for grapes. Because the gaps let air and light through, a trellis divides space without shutting it off — which is why people also use it as a screen to hide a rubbish bin or an ugly wall. The word is also a verb, though a much less common one: to trellis a plant is to train it up such a frame. From the criss-cross look comes a second use for the pattern itself — a 'trellis pattern' on cloth, on a cake, or on a window grille means those repeating crossed lines, with no plants anywhere near.