These Centre straps are made of 2.5mm Galv that keep the sleepers together. This method is cheaper than Concrete Sleepers produced by others. You can treat the (Recommended) Hardwood sleeper with old diesel oil. You can use treated pine sleepers if you wish but they will last about two years depending on your location.

Easy to drill from the dirt side, of your new wall using the strap as a template. Purchase some M10 x M100 Cup head bolts and watch the sleepers align themselves. As they are 1200 long, you can cut them and use them anywhere where they are needed. The holes are 11mm and staggered to suit a 200mm wide sleeper.