This excellent hardware for deck and porch railings is easy to install, unobtrusive and extremely strong, and also helps prevent moisture damage. The paired all-steel connectors for nominal 2x4 stock are sold in 90° and 22.5° versions.
Each connector consists of a formed base welded to a hollow shaft that is embedded in the rail end. Just cut a pilot channel with a hole saw, drive the shaft in (it's bevelled for easy insertion) and screw the base down. Only the base shows, leaving a tidy, finished look.
The connection is exceptionally strong since the shaft stiffens the join and is supported by wood inside and out. The base leaves space for air circulation and blocks water from wicking into end grain, preventing rot. Finished in an all-weather epoxy coat suitable for ACQ-treated lumber.
Each comes with mounting screws (3/4" hole saw needed).