Sometimes, I see dimension lines drawn like this:
Where there are extension lines and double-headed arrows between them. This is also how my textbook, Technical Drawing with Engineering Graphics, 15th Edition, has it, and this is what we were taught to do in class.
However, most of the time, especially in hand-drawings, I see them drawn like this:
Where there are no arrows, but rather slashes at each end. Whenever any of my lecturers are hand-drawing dimension lines, they always draw them with these slashes instead of arrows.
Is there any reason for these two different ways of dimensioning drawings? I can't seem to find any particular contexts in which either are used, except that when hand-drawing it's probably easier to do slashes instead of arrows. Then again, I've also seen the slashes in computer drawings.