<https://www.parktimber.co.uk/product/plained-square-edge/#product>
<http://schema.org/description>
"PSE stands for planed square edged as all surfaces and edges are planed to a smooth finish. PSE is suitable for a wide range of joinery applications where appearance is important and a clean finish is required. It is easy to work with. This PSE has been treated with Tanalith E.\r\n\r\nNominal sizes NOT finished sizes, so please deduct about 4mm for all sizes."
<https://www.parktimber.co.uk/product/plained-square-edge/>