Q. We just installed an 8 feet wide patio door. This door is a sliding door, (composed of a 4 feet stationary glass panel and the sliding 4 feet door). There is no middle column where to install a mezuzah. Placing the mezuzah at the left side of the frame is too far to reach when exiting the house. Could we place the mezuzah on the right when exiting?

A. Assuming your patio door opens to the back garden and you can access the garden from the street also, according to most Poskim the mezuza should be on the right of the entrance to the house from the garden, (Chovat Hadar 8, 1, 4), it is the only correct place for it.
If there is no access from the street to the garden, Igrois Moshe (Y.D. 1: 181)., maintains that you indeed place the mezuza on the right side, as you go out to the garden. See also Minchas Yitzchok (1: 8-9), Ohr Letzion (Y.D. 1: 14), Beis Yatziv (2: 1). However, other contemporary Poskim disagree. (Inside Stam, (p. 212) quoting Horav Eliashiv zt”l, Horav Vosner zt:l and Horav Nissim Karelitz Shlit”a).
Poskim maintain that you can place the mezuza on the aluminum frame of the closed glass panel, either at the internal edge or the outside, and that would make it accessible to be touched and kissed. You will then be treating that panel not as a door but rather as a wall.
Horav Shlomo Miller’s Shlit’a opinion is that, it is preferable to place the mezuza on the frame connected to the brick of the house, or on the brick itself. The reason being that sometimes, the stationary glass panel can be unscrewed from the frame and become mobile like the other sliding door, so it is not a proper wall. In addition, the aluminum frame of that panel is similar to a door and unlike the jamb of a proper door frame,
In you particular case, when dealing with the handicapped who desire to reach and kiss the mezuza, the Rov maintains that it can be placed on the aluminum frame of the always closed glass panel.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a