A Macro Etch test also known as a cut and etch test is a very valuable teaching tool. Its a destructive test but it can verify settings and technique and since you see the results in a matter of minutes, the puddle is still fresh in your mind. Did it penetrate like you thought? One Cut and Etch test is worth a thousand opinions
I ground off the corner of an aluminum cube project to demonstrate a technique for filling a hole. A gas lens cup helped for this task
Outside Corner joints on 11ga 6061 aluminum are enjoyable. This This Aluminum cube project is a good way to get some practice on outside corner joints.
Tanks, Reservoirs, Pontoons, can usually be repaired using a doubler patch that uses a lap joint