One can specify a box in LaTeX, using various methods for example:

```
 \newsavebox{\Abox}
 \savebox{\Abox}{\parbox{4cm}{\lorem}}
 \usebox{\Abox} 

```

How can I retrieve the width, height and depth of the box. TeX has the primitives `\wd`, `\ht` and `\dp`. However in order for these to be used it is necessary to know the number of the box for example `\box13`.