Structure of a crutch

A crutch, comprising

• (a) two hollow uprights joined together at lower ends, and bent such that upper portions thereof are apart and substantially parallel;
• (b) a crosspiece for a person to hold with one hand, the crosspiece including:
• (1) a main body up and down movably fitted around the uprights at two ends;
• the main body having a middle portion, and two end portions on two sides of the middle portion;
• the main body having two tunnels respectively lengthways extending along whole lengths of the two end portions thereof and capable of communicating with holes of the uprights;
• the main body having slots lengthways extending on the two end portions thereof and communicating with the tunnels;
• (2) two engaging pins respectively held in the tunnels of the main body in a linearly displaceable manner;
• (3) two elastic elements respectively positioned in the tunnels for making the engaging pins engage the uprights;
• (4) two connecting bars linearly displaceable along respective ones of two lateral sides of the main body;
• each connecting bar having first and second hooked ends, which point in opposite directions;
• the first hooked ends being respectively passed through the slots and connected to the engaging pins such that the pins and the bars will move together;
• (5) two control members respectively arranged on and linearly displaceable along the two end portions of the main body;
• each control member having a hole thereon;
• the connecting bars being respectively passed into the holes of the control members to engage the control members at the second hooked ends thereof for connecting the engaging pins to respective ones of the control members;
• whereby the engaging pins will be retreated away and disengaged from the uprights as soon as the control members are pulled further away from each other, thus allowing the crosspiece to be linearly displaced along the uprights.