External Edge Caulk Tool

You can buy plenty of tools (or just use a finger) to caulk an internal edge. These are readily available from a variety of hardware store sources. But...what if you have to caulk an external edge? Such as an external mitered corner or edge? There is remarkably little information on how to do this or what tools you should use. The only video I could find was a person who used a drywall knife.

Here is a tool that provides a gentle curve for caulking an external mitered edge such as on a shower curb. I printed it using TPU, which is recommended as it "gives" over any imperfections along the mitered edge.