Ramp Slide
Ramp slides are a decently versatile tech in which you slide down a non-walkable slanted surface to gain speed. You can also stall on some of these surfaces, depending on how slanted they are.
Execution
Compared to their namesake ramp slides are surprisingly easy to perform. All you need to do is line up with the surface and move towards its downwards trajectory. The gravitational force combined with the lack of ground and air resistance will accelerate you. If you wish to stall on the surface doing the exact opposite will yield results.
Pros and Cons
Ramp slides can provide a valuable speed gain without the need for a jump, meaning you will not trigger any wallride cooldowns. They are also a very useful tool to surprise attack your enemies, coming in from high above. They however, like so many techs, require special surfaces.
Tips
Although that is the case these surfaces are commonly found and exist on almost any map. Your best chance are rooftops and other geometry high up in the skybox.