同学们，上回我们介绍了邮票要素中的材料和刷色，今天我们来认识一下邮票的齿孔、背胶和水印。１８４０年至１８５４年的邮票都没有齿孔，自亨利·亚奇发明了齿孔机以后，邮票才出现了齿孔。现在常见的邮票齿孔多为圆孔，也有四方和六边等形状的齿孔。若按其状态来分又有光齿 Classmates, Last time we introduced the material and brush color in the stamp element. Let's get to know the perforation, glue and watermark of stamps. Stamps from 1840 to 1854 did not have perforations, and perforations were found in stamps after Henry Picky invented the perforator. Now common stamp perforation mostly round hole, there are four and six sides and other shapes of perforation. If according to their state to have another light tooth