It is an Keyed Tenon outdoor bench, also a nice Patio Furniture, which can be placed on the front porch for changing shoes. It has simple structure and is easy to build. Using the same structure, you can make it any length you want. There are gaps on the seat slat to drain rainwater.
Material Suggestion: Please use waterproof wood for outdoor.
If you want build the bench in different sizes, you just need to modify the length of the below 3 parts all together. (For example: all add 5" or all reduce 5")