Trolley rod now generally built-in, so the structural stability will be stronger, the external rod in the loading will be inconvenience, and very easy to damage, basically been eliminated by the mainstream of the times. Where possible, we also have to open the inside to observe the color of the inner tube, if it is black, it may be iron pipe. If it is white, then there may be aluminum tubes, our choice is inclined to steel, which has such a lever to withstand all kinds of pressure, Hold live a variety of scenes. When testing the lever, be sure to test the lock button several times, after pressing should be able to retractable, there is a very smooth sense of lubrication, after the rod outstretched to test the stability of many airport and train station building structure is full Stairs, up and down on the lever balance of operation demanding, it must be aware of judgment. In addition to remind everyone to note the handle bar handle, hard plastic material or give it up, very poor durability, the handle had to choose a soft, feel better.