Mechanical Anchors

Mechanical anchors in the form of manufactured products are a modern invention, with most of them relying on a mechanical wedging action. They suit a variety of different applications, and make many tasks far easier to carry out. In the past, timber wedges or other more labour-intensive solutions would have been implemented to achieve the desired outcome of a task. The mass production of these modern mechanical anchors helps to increase the speed of production associated with specific fixing tasks. Here are some of the most common types of mechanical anchors that are used in modern residential construction. 

Spring toggles/Toggle clips/Butterfly clips

Spring toggles are a form of mechanical anchor that are used for lightweight fixing applications into plasterboard. Often there are times when finished items like shelves or toilet roll holders need to be fixed to a wall towards the end of a job. With modern timber and metal stud partitions being a cost-effective building method in lieu of solid masonry walls, it’s not uncommon to have to fix components to stud walls. Quite often there may not be a stud directly behind where a fixing needs to be placed. Even if items are to be hung from modern masonry walls, the likelihood is that the wall has been dry lined with plasterboard, with a small void behind the plasterboard. In these scenarios, the only way of effectively securing items to the wall is to attach them directly to the plasterboard. This means some form of plasterboard fixing must be used.

These toggle clips are capable of holding on average up to 20kg per fixing depending on the size and manufacturing specifications. To install these clips, a hole must be drilled to allow the toggle to enter behind the plasterboard. This hole is typically around 10mm in diameter for standard fixings, though larger holes may be required for longer and larger fixings. With the hole drilled the toggle must be pinched together and pushed through the hole, with the toggle springing open again on the inside of the hole. The bolt can then be tightened, pulling the toggle into the back of the plasterboard. Before the bolt is fully tightened, the item that is being fixed must be placed over the head of the bolt. This can be done easily if the items feature a keyhole mounting design. If the item only comes with a single hole, the clip must be removed from the bolt before it is pushed into the hole. The bolt must be threaded into the hole and the toggle replace on the end of it. Then the toggle can be pushed through the hole and tightened. This is due to the fact that the bolt cannot be removed from the toggle once the toggle is in the wall, as it will simply fall down in the void. Bolts that have been fully tightened can sometimes be removed if the toggle is pulled far enough into the back of the board for it not to fall down the cavity if the bolt is removed. This is not the intended purpose of these clips though. The bolts come in a few standard lengths, most often 50mm or 80mm. They are very handy for lightweight fixing applications and are very quick to install.  

Plasterboard fixings/cones

Plasterboard cones are another form of plasterboard fixings that are more universal in their application, though they are not able to hold as much weight as toggle clips. These fixings come in two parts, a fixing cone and a screw. The cone is a tapered threaded aluminium insert that is self-drilling. It features a hole through the middle with a PZ2 slot cut in the top. The cone can be threaded directly into plasterboard with a driver and is twisted in until the flat head is flush with the surface of the plaster or plasterboard. At this point, the provided screw can be driven in and out of the centre of the cone in order to fix items to the wall. If the item or screw needs to be removed, the cone will still stay in place in the plasterboard, giving them an advantage over toggle clips. The provided screws are around 35mm in length typically though longer standard wood screws will thread into the cones if longer fixings are required. It's important to not use screws with a thicker shank, as this can cause the cone insert to over spin and strip out of the hole in the soft plasterboard.

Plasterboard cavity fixings/hollow wall anchors

These fixings are similar in concept to toggle clips and are also used for fixing into plasterboard. These anchors feature a central bolt that is threaded into an expanding sleeve with a washer head on it. A hole is drilled in the board to allow for the bolt and sleeve to fit through it. The washer on the top of the sleeve registers against the board, stopping it from falling in. The bolt is then tightened, which in turn begins to pull the far end of the sleeve towards the back of the board. The more the bolt is tightened, the closer the expanding sleeve gets to the back of the board, until eventually the sleeve is pinched in place on the board between the washer and the expanded sleeve. At this point the bolt can be removed without the sleeve falling away, and an item can be easily fixed to the wall with the bolt. The utility of these fixings is almost a cross between the plasterboard cones and the toggle clips. The bolts can reach around 50mm in lengths, with smaller options available. Plastic varieties of this concept exist that can be used in conjunction with standard wood screws. 

Rawl plugs/Wall plugs

Rawl plugs/wall plugs are a tried and tested method for achieving reliable and strong fixings into masonry or concrete. The wedging action of these plugs are very simple in concept, and they are a cheap and effective solution for securing components to masonry structures. The plugs are made of injection moulded plastic and come in varied styles depending on the specific manufacturer. For the most part, the colours of the plugs are standardised, with each representing a different size and diameter of hole that needs to be drilled. Many sizes of the plugs are available for use with different diameter screws, though the most commonly used in general construction and carpentry would be the 7mm brown plug. In order to use these plugs, a 7mm hole must be drilled into masonry to allow the plug to slide into it. The hole must be deep enough for the desired length of screw to not bottom out in the hole. When drilling into cavity masonry it's important to not drill all the way through the hole, as the action of driving the screw into the plug can push the plug out the back of the brick and into the cavity. Once the hole is drilled to the correct depth, the plug can be hammered into the hole until the top of the plug is flush with the brickwork. At this point, the desired screw can be slightly hammered into the hole in the middle of the plug and then driven in with a driver. As the screw is driven into the centre of the plug, the plastic expands outwards and wedges against the inside of the hole. If installed correctly, this wedged plug is very firmly fixed in the wall and is very resistant to draw out. When using these plugs to fix materials to masonry, the hole can be drilled through the material and into the masonry. The plug is then driven through the face of the material until it is flush with the surface of the material. The screw is then hammered into the centre of the plug until the plug is pushed through the material and into the hole in the masonry. The screw can then be driven in as usual. The downside of these plugs is that they may not always grab in crumbly materials. If plugs are not properly grabbing in softer material, a smaller hole can be drilled, and the plug can be forced into the hole. This usually works.

Hammer fixings

These fixings are an adaptation of Rawl plugs, with a central piece of utility that is a cross between a nail and a screw. A hole is drilled to the correct size for the plug on the end of the nail/screw. The top of the nail/screw can then be tapped with a hammer, inserting the plug into the hole and continuing until the head of the nail/screw is flush with the material that is being fixed. The wedging action of the nail/screw in the plug grabs the inside of the hole and is resistant to draw out. If the nail/screw must be removed, a PZ2 bit can be used in the slot at the top to drive it out. The very shallow thread of the nail/screw means that they cannot be driven in and out like a screw would be able to. Overall, these are a good piece of utility for the fast installation of numerous wall plugs.  

Expansion bolts

Expansion bolts are a more heavy-duty structural solution to achieving solid fixings into masonry. There are a few different designs of these bolts, though they all follow the same general concept. The fixing consists of a bolt that has a reverse wedge-shaped nut threaded on the end of it. The bolt is surrounded by a thick expanding sleeve. The correct sized hole for the sleeve is drilled into the masonry, deep enough to allow the bolt to be fully seated. The bolt is then tapped all the way into the hole until the head meets the surface. The head of the bolt is then tightened in the hole which slowly pulls the cone upwards. As this happens, the sleeve is pushed apart and wedged into the sides of the hole. The bolt should be tightened until the sleeve is firmly in place in the hole. At this point the bolt can be removed, leaving the sleeve wedged firmly in place. An item can then be fixed to the surface of the masonry by threading the bolts through it and back into the hole and sleeve. These fixings are used for heavy duty structural applications and are corrosion resistant for use in exterior scenarios.