It's important to balance your quadcopter drone before flying. If it's not properly balanced, it will not reach its best performance as the motors will be running partially just to overcome the imbalance and keep the quadcopter level. 3D print this balancing tool and get the most out of your hobby. If you build one of these and find it useful, please post a print and follow us.
To see how to balance a quadcopter, watch this short tutorial: https://youtu.be/Sqqb21iHwC8
The office style push-pins required are standard variety such as these*: https://amzn.to/2Dgzfo2
Check out our other work at http://www.3drebeldesign.com
You may have to clean and possibly sand any burr off the sliders, so that they slide smoothly. Insert a push-pin into each slider and secure with small amount of glue. The rubber band should be snug but not so firm as to push the pins deeply into the plastic of the quadcopter. It only takes light contact and after many times of use on the same drone, the scuffing seems to be only superficial if any. Since you may not have the same elastic bands available, there are several possible positions for the elastic to sit and adjust tension.