How do the ends of the sofa or shelf legs make contact with the floor?

Felt appears repeatedly at the tips of the legs.

The legs of the Lay Sofa are oval pipes with straight surfaces, and leveling feet containing felt go into their ends^[1]. These leveling feet level the sofa and reduce damage to the floor^[2]. Regardless of whether you choose the Fabric or Leather option, the configuration under the feet is the same^[3][4].

Because the Truss Shelf has many legs, its method is slightly different. Dedicated plastic foot caps are first fitted onto the ends of all legs, and soft felt is attached on top of them^[5].

Generally, leveling feet are parts that finely adjust height by turning screws, so they are used to eliminate wobbling when the floor is slightly sloped or one side is lifted. Felt is a material made by pressing and hardening fibers, which reduces friction with flooring; however, with prolonged use, it can become compressed or collect dust and lose its effectiveness, so it is good to check its condition once in a while when moving furniture. If heavy furniture is pushed to move it, the felt may slip and peel off, so it is safer to lift and move it.

hmmm, these are areas that are hardly noticeable once you sit down or place items on them, but it is notable that both products have finished those tips separately.