Match drilling is when you have a part who’s hole needs to be transferred to another part accurately. You clamp the part with the hole’s correct position on top of the part that needs a hole to except a bolt to bolt the two pieces together. Then transfer punch the location and drill straight through the lower material. it is a good idea to do this process in two steps, starting with a drill smaller than the desired hole size. Then re-drill to the correct size while still clamped together. This will tend to eliminate an oblonging of the top hole you are essentially using as a drill bit guide during the process .