Lines can have a vfill \vspace{\fill} in the middle.
Lines can have a protected vfill \vspace*{\fill} in the middle.
Lines can have a vertical absolute space \vspace{2cm} in the middle.
+Lines can have a baselineskip \vspace{1.2\baselineskip} in the middle.
Lines can have a vertical relative space \vspace{0.09\columnwidth} in the middle.
Lines can have a vertical glue-length space \vspace{2cm minus 2bp plus 1cc} in the middle.
Lines can have protected vertical space \vspace*{2cm} in the middle.