Abstract: In the maintenance of the transmission line, the closed card is often used to replace the single -piece abnormal insulator. This article first analyzes the defects of traditional closed cards; secondly, the design process of universal closed -type cards is explained, the use of universal closed cards on -site operations, and analyzing the application effect of the application combined with actual cases; Finally, the development and application of universal closed cards summarized and put forward further improvement opinions. The general-purpose closed card can be used to replace the 70-240 kN of various types of porcelain and tempered glass insulator, and reduce the operation time on the tower by about 58%, which greatly improves the operating efficiency.