Using a hollow tube, they drill into the tree and extract a 5-mm wide cylinder that shows each ring starting with the most recent, just under the bark.

VOA: standard.2010.04.05

to take my cylinder now, and the external pressure and the internal pressure are not going to be I'm going to start with my cylinder here, I'm going to put little pegs here so it doesn't fly up.

活塞内外的，压强不相等,我们在,放上插销，以防止活塞。

麻省理工公开课 - 热力学与动力学课程节选