When it comes to going off road with your 4x4 doing damage to your body work is not something most people enjoy. When you're travelling over rocky or steep terrain, your 4wd's door sills are open to scraping and denting from rocks and other obstacles. Unlike normal alloy side steps, rock sliders are designed to protect your sills from large obstacles which cause damage.
The difference between side steps and rock sliders is that rock sliders are often made from steel and are designed to withstand the damage caused by hitting obstacles on the track. A normal alloy side step will often bend and buckle on even a slight hit or scrape.
Often times rock sliders will, as the name suggests, let you slide over rocks that your ground clearance may not allow. It is important to invest in a set of good quality rock sliders or make up a set of your own if you're handy with a welder. These will save you the hefty bill from the body shop repair man should you slip on the track and hit a boulder or log.
As always, be careful when on the tracks and hope not to hit anything, but having the protection there will help you sustain some impacts with obstacles without causing damage. Not to mention, your 4x4 will look super tough with them on!
Rock sliders will mount directly to the chassis rails. Often they have a bracket that forms a U shape around the chassis box section providing the sliders with plenty of strength to support your 4wd when it's stuck on a rock. Rock slider mounts should be strong enough to allow the vehicle to be raised by a jack underneath the slider.
Rock sliders should have 3 or more mounting points along the chassis and they should be equal thickness and diameter tube as the slider itself. The stronger the mounts are, the better chance of surviving impacts they will be.
Most rock sliders use at least 3mm thickness steel tube. Tube is recommended over box section as it is stronger and will withstand more force. If you make your sliders out of anything thinner you will find the sliders will dent too easily. Thicker steel us often used for the mounts to the chasses as there is a lot of pressure on these points.
It is up to personal preference as to what style of mount you wish to use for your sliders. Bolt on is more common as it allows the sliders to be removed as required if repairs to the vehicle are needed.
There are many different manufacturers of rock sliders around and you are likely to find a decent set to suit your needs and budget.