When you select this tool, , the arrow cursor changes to a pencil that can be used to enter this object in the Main Window.

Click your mouse button when the pointer is located where you want to put the upstream end of the multi-channel, a link used in DRAINS to allow for complex multiple pipes connecting the same points. The channel will appear as you move the pencil. Clicking again will fix the downstream end.  Both ends must be anchored to a node, detention basin or other device.

To enter data, right-click while holding the mouse pointer on a point along the channel to open a pop-up menu.  Selecting Edit Data
 from this opens the Multi Channel property sheet, from which you can specify various combinations of open channels and pipes.