As an antique the lap desk is a smaller variant of the writing slope. It is also called a writing box or a writing cabinet. In certain instances it is known as a portable desk, a term which is usually applied to larger forms. Most antique lap desks are really meant to be used on a table or some other stable surface. They are often strongly built of fine hardwoods like mahogany or walnut.
They were, in effect, the fore-times equivalent of a PDA -- that is, they supplied, to the traveller, many of the conveniences of carrying round an entire escritoire. From them has come the concept of the briefcase not just as a carrier for papers, but as a portable writing place, and thus the laptop computer.
As a modern form the lap desk is meant primarily for use in bed and other similar circumstances. It is also known as a bed desk. There is a wide variety of forms available, but as a rule it is much smaller and simpler than the antique lap desk, having at the most a small drawer or holding area for a ballpoint pen and a pencil. It is also made of much cheaper materials, save for a few craft productions.
Certain lap desks have a removable monopod, which makes them collapsible cousins to the lectern desk. Others have two short collapsible legs, so that they can be used both in bed and on a lap, when the legs are folded. Finally, some come with a built-in battery powered lamp, continuing the tradition of those antique lap desks and writing slopes which had swinging or hinged brass candle holders built in.
Most modern lap desks are considered specialty items and very few furniture dealers keep them in stock. They are present, however, in a large number of catalogues and on some commercial Web sites.
See also the list of desk forms and types.