[Therion] Height numbers in square boxes

[Bill Gee]

Hello everyone -

A common convention around Missouri cave mapping is to indicate the height 
change of a floor step by enclosing the value in a square box.  This is not 
the same as ceiling height which is enclosed in a circle or oval.

I have been using the object "point height" for this.  It works except there 
is nothing around the value.  It just hangs out in space, so to speak.

I used the "-d" option to dump all the MetaPost and TeX code.  I find no 
references in any of the files to objects of type height or passage-height, 
which implies that these two objects are not generated by MetaPost.

Is it possible to redefine the "point height" symbol so it draws a square box 
around the value?

Thanks!
-- 
Bill Gee