An example security gate can include: an outer frame; an outer gate disposed within the outer frame, the outer gate defining a plane and having a plurality of outer gate vertical members, and the outer gate defining an inner gate opening; an inner gate disposed within the outer gate, the inner gate defining a plurality of inner gate vertical members, wherein the inner gate is configured to move vertically within the plane to control access through the inner gate opening, and wherein the plurality of inner gate vertical members are sized to telescope within the plurality of outer gate vertical members as the inner gate is moved; and a locking mechanism to lock the inner gate at a vertical position relative to the outer gate to define an accessible size of the inner gate opening.