It depends on the way in which they are written.
4 and 7 clearly have horizontal and oblique lines.
The number 1, in some fonts (like this one), also has both.
All the rest have sections that are horizontal and those that are oblique.
The letters T and L are formed as asked.l and t from fiona1234
C. I. H. F.
The letter - H
5 line segments
5 line segments
Oblique
None, as far as I can see. Which, given that I cannot see any triangle, is not saying much!
a line that is neither verticle or horizontal
An oblique line can be diagonal, sloping or slanted. It is not vertical, horizontal, parallel or perpendicular.
8
Oblique is neither vertical nor horizontal to a given line or surface
AKMNRVWXYZ
I
Letters that have a vertical line symmetry: WTYUIOAHXVM Letters that have a horizontal Line symmetry: EIODHKCB
E
Z
Letters that have parallel line segments are H, E, F, M, and N