Apple IIe Card - Manual (Page 30)

2. Connect the Apple 5.25 Drive cable to the larger of the two
remaining connectors on the Y-shaped cable, as shown in
the figure.
Again, be sure the D-shaped connectors line up correctly, and tighten
the connector screws to ensure a proper fit.
▲
Warning: If you want to swap drives or devices connected to the
Y-shaped cable, be sure to turn off the computer first. If you change
devices while the computer is on, you may damage the device or
the computer, or both.
▲
Chapter 1: Preparing the Equipment 14