Shiplap can be used for many things, but it's often found on interior and exterior ... in materials between tongue and groove ...
The 3/4-in. thick baseboard protrudes 3/16 in. past the 9/16-in. thick paneling, creating a nice-looking ledge, or reveal (Photo 7). If your tongue-and-groove paneling is 3/4 in. thick instead, shim ...