The back mark is the distance from the back of an angle or channel web to the centre of
a hole through the leg or flange. This dimension is selected taking into account, access
for tightening the bolt using an appropriate spanner, being close to centroidal axis ,and provision of required edge distance
The distance between centres of holes in flanges of joists, universal columns and Universal beams is selected
to provide accessibility and acceptable edge distance.
Remember - the information on this site is for general information purposes only and while we endeavour to keep the information up to date and correct, we make no representations or warranties of any kind, express or implied, about its completeness, accuracy, reliability, suitability or availability. Any reliance you place on such information is therefore strictly at your own risk.
Roy Beardmore passed away on 9th March 2013. He is sadly missed. This website, Roymech, has been an invaluable resource for engineers around the world and we hope to maintain this incredible legacy going forward.