The balcony railings are the beautification and protection facilities for the outer edges of the balconies, which are welded or assembled from alloy pipes. The common low window ledge is about 0.5 meters away from the ground. If the fence or fence is increased by 0.4 meters next to the interior wall, it will surely meet the regulatory requirements. If the window sill is too large, such as a bay window, children often stand on the ledge, and the user must also stand on the window sill to open the window. At this time, the height of the guardrail attached to the window sill should reach 0.9 meters.