Choose Home tab→Solids group→Thin Wall list→Vent 
.
Select a closed sketch element that defines the exterior boundary of the vent, then click the Accept button.
Select one or more sketch elements that define the ribs, then click the Accept button.
Select one or more sketch elements that define the spars, then click the Accept button.
Click to define the extent direction.
Click Finish.
Note:
The sketch elements for ribs and spars can be any valid combination of open and closed sketch elements.
You can use the Vent Options dialog box to set the vent properties you want. For example, you can define the thickness, extension, offset, depth, and draft angle for the ribs and spars.
You can also specify that fillets and rounds are included in a vent feature.