Now that the value of models in the teaching of Geometry has received emphasis in the Report on the Teaching of Geometry in Schools, a great impetus may be expected in their development. This expectancy combined with the article by Mr. Langley (Math. Gazette, May 1924), has led the writer to think that some account of a device for three-dimensional representation may be of interest to readers. In its present form the model is so arranged that figures for very general straight-line problems can be built up in a very few munites. It has been in active use for about a year and has proved of valuable assistance both in trigonometrical and in pure geometry.