Vertical height (vmtx)

How can I adjust the vertical height of glyph to zero?
I searched it on web and someone told me to edit the vmtx table, but i didn’t find this table in GLYPHS
and i just wanna change some of them ,not all glyphs.
plz help me. thanks!

In Edit View, you can switch to the vertical writing mode. Then you can edit the vertical metrics in the info box.
In font view, in the Details View (lower left), click the “H” icon to switch between horizontal and vertical metrics.