Tools you will need:
- bolt cutter
- small flat-head screwdriver
- small hacksaw (I used a coping saw)
- some bolts (small thread, M2.5 or 0.1" thread diameter)
- some screws
- ruler & pencil
The only requirements for the existing drawer:
- approx 12mm (0.5") clearance on either the left or the right of the drawer (almost any rail system will have this)
- approx 9mm (0.35") clearance behind the drawer
The drawer can be made of wood or metal - doesn't matter.
Note about the small piston-type door buffers / dampers:
Before this project I attempted to use these to damp my drawers, but they didn't work well (drawers wouldn't self-close, or still slammed shut.) The Blumotion system with its long throw and spring+latch mechanism overcomes these issues. Thanks to adamazing for bringing this up in the comments.
Step 1: Obtain the Blumotion mechanism
WARNING #1: IKEA also sell an AU$10 RATIONELL damper add-on kit. This will NOT work as it contains only the damper and not the spring-latch mechanism which is so crucial to the system.
WARNING #2: Don't buy the bigger drawers as they use a different damping mechanism which is much harder to modify.
Obtaining this kit from IKEA is relatively straightforward. If you need a salesperson's assistance when ordering the kit(s), you will probably be asked if you have the correct RATIONELL cupboard in which to install the drawer - a lot of people have obviously tried to screw their existing drawers onto the RATIONELL rails with little success.
Once you have purchased the kit, take out the 2 rails and set the rest aside.