Place Individual MEP Elements
You can build up the desired mechanical system by placing individual elements one by one:
•Select the desired tool and place the first element.
•Select the tool of the next element to be placed. Ensure that the right placement hotspot is set (the placement hotspot is the square one, in the 2D Symbol preview in the Preview and Positioning Panel).
•On the Floor Plan, click at any available connection point (indicated by a checkmark cursor) on the existing element.
The elements will connect correctly. The second element - while using the default settings of the active tool - will nevertheless adopt the connection geometry of the first (already placed) element. Connection geometry includes (as applicable): shape, height/width, thickness of element wall, connection type (e.g. flanged or not): these are the same parameters you set in the Connections tab page of the element’s MEP Custom Settings tab page.
You can add additional junction-type MEP elements to a placed straight segment. (Junction-type tools are the Tee, Wye and Take-off.)
Note: The Duct Wye can only be placed onto a straight, horizontal duct segment.
Adjust the element settings, then click on the placed element. The elements will connect correctly. Depending on the geometry of the newly placed element, additional clicks may be necessary to define its placement.
For example, when placing a Duct Tee onto a regular Duct segment, you will click anywhere on the regular Duct’s centerline:
Next, you must choose one of four possible positions for the Tee branch: should it branch off the right, left, top or bottom of the duct? Move the cursor around, then click in one of these four positions to choose the desired geometry.
Right 
Left 
Top 
Bottom 
See also Start Routing by Placing Junction on a Placed MEP Element.