Here's the symbol set with some more samples. 12 should be the one that you have asked for, Hacker.Hacker wrote:... Could you please draw one similar to 7, but with the small rectangle centered? Just to see how it looks.

For reference, images are numbered, now. 1, 2 & 4 have been substituted by other.
- The ones which I don't like: 4, 6, 10, 12
- 9 doesn't look that nice since it's not centered, 10 is too small.
- My favourite: 2 (same as 7 but filled with some grey)