I have a plastic toolbox that I want to mount on the wall. I need it to be extremely stable once mounted, and I was therefore considering simply screwing it directly to the wall. However, I'm concerned that I might crack the plastic. What would the best way be to do something like this? The toolbox is made from a softish plastic, so that's why I was even considering drilling through it.
If you do decide to attach with screws you should use what are called fender washers between the head of the screw and the plastic. The fender washer has a larger diameter than a normal washer and is meant for situations where you need to spread the force of the screw over a larger area. This will make it less likely that your screw will crack the plastic or pull through. Additionally. When tightening the screws slow down as you get close to full depth and gently bring the screw to full tightness against the washer and plastic. This will minimize the chance that you will create cracks in the plastic with shock. if your box is made from a brittle plastic it might not hold its own weight with out cracking. In this case a small piece of wood that would span between two holes that you could screw through to hold it to the wall. This would create a larger clamping surface and spread the forces over an even larger area than the washers. If none of this makes sense it would help if you could describe the box a little bit or even supply a picture.
If the tool box is not actually designed to be mounted to the wall then there is a strong possibility that doing so may deform the box so that it does function in the way intended. This could be especially true if the box has a hinged lid. I think that your best bet would be to build a small shelf for under the tool box and secure that into the wall studs. You could then secure the box to the shelf possibly by even gluing it in place. Gluing the base of the box to the shelf would have far less chance of deforming the shape of the thing. Using a shelf idea also allows easier adjustment of where to place the box so that a possible lid does not interfere with the wall.
while i agree with the shelf solution, i would approach a little differently, use both the bolts into the wall and a simple L shaped flat iron bracket..
So basically get two L shaped Brackets, and let the one side of each bracket support the bottom of the toolbox. then put a hole in the top half of the other side and let this run along the wall. the toolbox can then sit on the brackets and you can drill and put rawl bolts through the toolbox side, then through the hold of the bracket then in the wall...
I would also use the fender washer or a base plate on the toolbox side to ensure that you dont break the toolbox. .
The brackets (and essentially the holes in the toolbox) should be as close to the edges of the toolbox as possible for rigidity.. or alternatively... get a piece of wood to span from one end to the other inside the toolbox and then use that as your "fender washer"