In simple use TVPLOT will draw lines. Use just L=l, or just P= for the default center, or two P=(r,c) endpoints to ignore the default origin. Use SCALE if you mean arcseconds for L and not pixels, PA to rotate, or OFF to give an offset in whatever direction the X axis is for any PA specification. TICKS will give nice scale marks on the line.
Show the image subsection boxes (see BOX) with BOX=n. You can also make up any boxes just for plotting by giving the BOX keyword. This tells TVPLOT to think about BOX plotting instead of lines. Use W and H with the default center or C= keyword, two P= keywords to give opposite corners, P and C together for corners, any of L, W, or H by themselves for square boxes, and so on. Use PA, OFF, SCALE to help out.
Other symetrical plots. Here you have CROSS, CIRC=r, COMPASS=r, all of which follow the AXES, C=, or P= centers. Use PA, OFF, SCALE here, too.
Now you can make any label you want with the TEXT option - except you can't rotate it with PA (sorry - it uses system fonts that I didn't want to muck with). Use P=, or C= to position it - where you give where you want the center of the string to be. Right now VISTA has a little trouble with multiword strings enterred directly on the TVPLOT command line, but they work fine if you load them first with the STRING command.
Examples:
YDIM=25
XDIM=15
FUNNY=37
STEP=5
DO Y=-YDIM,YDIM,STEP
TVPLOT P=(-XDIM,Y) P=(XDIM,Y) PA=FUNNY
END_DO
DO X=-XDIM,XDIM,STEP
TVPLOT P=(X,-YDIM) P=(X,YDIM) PA=FUNNY
END_DO