\dashbox ¶Synopsis:
\dashbox{dash-len}(rect-width,rect-height){text}
\dashbox{dash-len}(rect-width,rect-height)[position]{text}
Create a dashed rectangle around text. This command fits with the
picture environment, although you can use it outside of there,
because lengths are numbers specifying the distance in terms of the
\unitlength (see picture).
The required arguments are: dashes are dash-len units long, with the same length gap, and the rectangle has overall width rect-width units and height rect-height units.
The optional argument position specifies the position of
text; see \makebox (picture) for the values that it can
take.
This shows that you can use non-integer value for dash-len.
\put(0,0){\dashbox{0.1}(5,0.5){My hovercraft is full of eels.}}
Each dash will be 0.1\unitlength long, the box’s width is
5\unitlength and its height is 0.5\unitlength.
As in that example, a dashed box looks best when rect-width and rect-height are multiples of the dash-len.