In TAD you can intermix freely both 2D and 3D. The reason is that you may be in the initial stages of designing, and you may not have yet decided the value of this property.

The level property indicates at which level is this object to be placed. Once both the level AND the height is set for a particular object then that object is internally treated as a 3D object.In TAD, there a two ways where both level and height (and a few other properties) can be given.

The value of level can be zero or negative. Read also the topic on height for more clarity.

Tip
When specifying the numeric value for this property, you can easily give a full mathematical expression here instead of the final value. You can even inter-mix ft and inches too! Internally, all ft and inch are converted to meters. TAD strictly uses the metric system internally for all the eventual values.

For example; if you give 0.3+1'3.25“ It will use the value as 0.68735 That means it intelligently detects 1'3.25” and converts that part into meters.

IMPORTANT Read more about a process called pinning here because you may think that the level from which the object is extruded to the height given for the class/object is from the true ground. Not necessarily! The said class/object could be placed not on the true ground but instead it may be placed on another surface.