Plans Pro autofills spaces using a custom algorithm created for each space type. The algorithm places furniture and doors based on a space’s access to circulation, relationship to building elements like columns, the size and shape of the space, furniture size, etc. 

There will be a number of ways the algorithm can fill the space. To cycle through all of the possible ways to fill a space, select a space, then click the arrows on either side of the 'autofill' button.  

To turn autofill on and off for specific space, select the space, then check or uncheck the 'Lock the space layout when editing space size or placement' box on the right-hand panel. 

'Lock the space layout when editing space size or placement' checkbox is automatically checked / autofill is disabled when you edit, add, or remove individual furniture in a space.