1) The Sisterlocks (tm) Clip Tool is designed with a spring hook to latch onto a lock and then you feed it through the base of the lock.
Disadvantage of Clip Tool: If the dreadlock is dry and brittle, the spring action of the clip can break the lock completely off. One of the Sisterlocks Certified consultants clipped the tool to my lock without any regards of the spring action of the hook, and I swear that my lock broke completely off where the clip tool was attached. The consultant apologized to me about the lock snapping off and then moved on to the next one. So no, I am not fond of this tool. People should be cautious to gently attach the hook to the lock.
2) A Safety pin has been suggested by Stylist Jovan on youtube. You actually just pin the safety pin on the end of the dreadlock and feed the smooth end through the lock as if it was the Sisterlocks "clip" tool.
Disadvantage of the Safety pin: Piercing through the lock over the course of a year may weaken the lock, and the closure end of the safety pin may accidently catch some hair if one is not careful when feeding it through the roots of the locks.
3) The hair pin: The coolest method yet! It is a partial feed through the base of the lock. Youtube channel Chocolatemilk0104 has a video to teach you at https://www.youtube.com/watch?v=RlWTWiLBqQo
Disadvantage of the hair pin: If your lock partings are smaller than the width of hairpin, then this method may not work because the hair pin would be too wide.