What is used to tuck under roof shingles when adding a metal patio cover?

What is used to tuck under roof shingles when adding a metal patio cover with ridges on it? So obviously I cannot tuck the metal roofing with ridges under the roof shingles so is there a certain metal that they sale to tuck under the roof shingles and take shape of metal roofing also? If so what is it called? I seen the metal that they use for ridges on metal roofs but that has a hump on it and dont think that is what is used in my case.. Please post..