Correct

盖戳

/ gài chuō / 
Strokes

Example

As a Verb

affix/set a seal; postmark

1
Wénjiàn
文件
gàichuō
盖戳
cái
才
yǒuxiào
有效
  
。

The file is valid only when signed and stamped.

2
Gěi
给
xìnjiàn
信件
gàichuō
盖戳

postmark letters