This section is from the book "Modern Buildings, Their Planning, Construction And Equipment Vol6", by G. A. T. Middleton. Also available from Amazon: Modern Buildings.
When thewhitewasher,plasterer, painter, or mechanic requires to reach a few feet, say 10 to 15 feet, above ground he uses trestles to enable him to erect a platform from which he can work (see B, Fig. 203). They are usually made of yellow deal. The sides, 4 1/2 inches by 1 1/4 to 1 1/2 inch thick, are bevelled at top and bottom.
The rungs are placed at uneven distances apart, to meet varying requirements as to height of platform. The trestles should be made sufficiently wide to hold three boards at least. The rungs are mortised to the sides. The hinges should be of strong wrought iron, and shaped as shown.