For an explanation of their use, see the chapter of The Unicode Standard on the Miscellaneous Technical block (http://www.unicode.org/versions/Unicode5.2.0/ch15.pdf#G12269).

As for U+23B0 and U+23B1, I discovered that Mono have them with glyphs suitable to go as they are in Serif.

For U+23B2 and U+23B3, I think their height should be reduced not to make the assembled sigma distorted.

⎰ = U+23B0 UPPER LEFT or lower right bracket section
⎱ = U+23B1 upper right or LOWER LEFT bracket section
Both one atop the other as above form a left curly bracket
⎱ = U+23B1 UPPER RIGHT or lower left bracket section
⎰ = U+23B0 upper left or LOWER RIGHT bracket section
Both one atop the other as above form a right curly bracket

⎲ = U+23B2 summation top
⎳ = U+23B3 summation bottom
Both one atop the other as above form a big U+2211 N-ARY SUMMATION

For scan lines, these are characters found in VT100 and similar terminals, where there are only 9 scan lines to draw characters. See the pictures at http://vt100.net/dec/vt220/glyphs, these are the five characters at the top of the second column. So scan line-1 is at the top, scan line-9 at the bottom, and scan line-5 is really U+2500.

This is from Jacob Poon's report of 2007-10,
https://savannah.gnu.org/support/?106274

Parentheses in Miscellaneous Technical (U+2300-23FF) have different font weights than the rest of the font. In addition, many of the glyphs do not have proper stroke terminators for the font family.