What you have is an old desk back when we used manual typewriters. There should be a heavy spring under the shelf where you have your sewing machine. To lift you pull the shelf out as far as you can then, with your hand on the outside edge, lift the shelf up. It should lock in place. I believe you just reverse the procedure to get the shelf down and pushed back in place to close the door. If you can get it to do that you should be able to to stand your sewing machine erect on the shelf at all times. Brings back a lot of memories seeing that old desk.