Thirty spokes meet at a hollowed-out hub;
the wheel won't work without its hole.
A vessel is moulded from solid clay;
its inner emptiness makes it useful.
To make a room, you have to cut doors and windows;
without openings, a place isn't livable.
To make use of what is here,
you must make use of what is not.
Which basically sounds like some sort of Zen koan. The illustrations make sense. If you have a vase, for example, it's hollow inside. If it wasn't hollow, it wouldn't be usable. If you have a room with no doors or windows, either, then it's not usable. The hollow spot in the vase and the hollow spot in the room (in the form of doors and windows) make this objects useful. Thus, something that is not there (the empty space) makes the object that is here (the vase, the room) useful.
Most of the various translations are very similar, especially in the first half dozen lines. There are some variations in the last two.
Gain can be had from somethingness,
But use can be had from nothingness. (Herrymon Maurer)