In 2019 version, we can delete surface by right click and Edit Sketch to delete a surface. In 2020 version, the function doesn't exist any more. You need bypass the step by Ctrl + left click to select all lines. After that, suppress the surfaces using right click + suppress physics.
Watch video Chapter 3: create beams without deleting surface function in 2020 version. online without registration, duration hours minute second in high quality. This video was added by user Tangible engineering 18 February 2021, don't forget to share it with your friends and acquaintances, it has been viewed on our site 374 once and liked it 2 people.