\makebox(width,height)[position]{...}
The \makebox command for the picture environment is similar to
the normal \makebox command except that you must specify a
width and height in multiples of \unitlength.
The optional argument, [position], specifies the quadrant that
your text appears in. You may select up to two of the following:
t - Moves the item to the top of the rectangle
b - Moves the item to the bottom
l - Moves the item to the left
r - Moves the item to the right
See section \makebox.