A touch plate can make it quicker and easier to find your origin point on your material. There are a lot of different types of touch plates, but the vast majority use some sort of metal block that detects when your end mill makes contact with its surface by completing a circuit.
Among touch plates, you can find ones that measure just the Z-axis or some that can also find the offset between the X and Y-axes as well. Locating in the X and Y-axes is a nice additional feature, but it doesn’t work for irregularly shaped bits such as v-bits and dado bits due to their inconsistent diameter along their height or radius.
The Sienci Labs Touch Plate is an excellent example of a touch plate that lets you find the corner of your material in all three axes automatically. The full written guide on getting it assembled and ready to use can be found here: Setting up the Sienci Labs Touch Plate