An Ordnance Survey cut mark in the UK. The term bench mark, or benchmark, originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a bench for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future.
The forces that cause windows to leak fall into three categories: house design, installation, and maintenance. Turning to the wisdom of industry experts, we can identify nine of the most common errors that occur during window installations, which can lead to window leaks â and now you can too.
What could be causing leak in upstairs bay window? There is a thin long wet patch in the front of the bay window (along the crease of where the roof meets the wall), also we have now noticed wet patches under the window sill (on the inside) in the joins of the bay window which are now spreading along the wall (into the middle of the bay).