when removing the guard rail from the main sheet of decals, make sure you cut one side deeper and not flat, you're not after a perfect guard rail however where you will remove these from cutting points make those cutting points as long as the decal sheet will allow you, the idea - it really is a pain securing the guard rail to almost nothing, so what I do is cut one side flat, the bottom side leave the cutting area leave as long as possible, hold each cutting point and bend these 90% this greatly increases your glue area. 
