There are two Stabilizers on each t?blade system: One holding the six screws and one holding the nuts. The one with the screws goes on the inside of the foot (if its the left skate the screws go on right side of it and vice versa). They function kind of like washers and make it easy to put the screws and nuts in the right places and to switch Runners quickly.
This is how you handle the Stabilizers to change your Runners: Unscrew each screw with your t-blade screwdriver without taking the Stabilizer out of its socket. Now use the screwdriver to push each screw back into the Stabilizer to press the nut on the other side out of its fitting. This makes it easy to remove both Stabilizers and take out the Runner. After inserting the new Runner into the Holder place the Stabilizers with the nuts in its socket first and then push the nuts fully into the openings. Now the Runner is steadily in place already and it is easy to put the Stabilizer holding the screws in its place and tighten the screws.