Using standard white board and L shape brackets I have for the first time been unable to complete the job and in fact have likely created a problem. The wall is stud/false made of cement? ( the dust is grey but could be plaster?). It seems to be something like 1 to 2 inches thick. Immediately behind is a solid brick wall. I first tried traditional rawlplug and screws which were 1 3/4 inch long but they just fell out of the holes with the shelf attachedThen I tried Toggle bolts. I have drilled the holes slotted in the toggles, screwed the brackets up really tight but there was still movement. As well as not being able to tell if there is any space at all between both walls for the toggles to sit, I could not understand why they remained visible at the front edge of the hole? I thought they should go back to where the gap is so they can open up?. The size of these are M4 x 50mm with a fitting clearance of 9-20mm. Any suggestions how to remedy this taking into account the size of the wretched holes I now have!!! Thank you.