Demarcation Rail Fence

By Huu Khanh Nguyen · Updated October 28, 2026 · timber, fence, demarcation, rail, half round rail, post and rail, boundary, highway, knee rail, bollard

A low fence of square timber posts carrying a half round rail on their tops, used to mark a boundary without enclosing it. Post size and height Rail size Post spacing Timber species or colour

Parameters

Name	Default	Unit
Run Length	6150	mm
Width	Math.max(postWidth, railFace)	mm
Height	postHeight + railFace / 2	mm
Bay Width	1500	mm
Distribution	count
Post Width	150	mm
Post Height	500	mm
Rail Face	150	mm
Finish	white
minPitch	Math.max(postWidth, railFace)	mm
span	sizeX - postWidth	mm
nominalPitch	distribution == 'distance' ? bayWidth : bayWidth + postWidth	mm
bayCount	Math.max(1, Math.ceil(span / nominalPitch - 1e-9))
lastBay	span - (bayCount - 1) * nominalPitch	mm
merged	distribution != 'count' && bayCount > 1 && lastBay < minPitch