A sliding dovetail is a strong joint for preventing movement in one direction. It can be created with ease in SketchUp.
You can get creative with how you want to make your sliding dovetails. Like everything else in SketchUp there are many ways to reach the same destination. You can create both parts and use intersecting faces to transfer the cutouts to the other piece. You can draw each shape individually and use the push/pull tool to cut them out. Or however else you can think of. The video above will walk you through one of the many ways to make a sliding dovetail joint.