sp help has a little on the subject:
Specifying Levels for Deck Items
Specifying levels in the deck plan allows you to create a deck system whose various parts are tied together as a unit having the same offset, offset direction, and depth and width of joist.
When first drawn, deck items (ring joists, floor joists, decking) are placed at level 1. When creating decks with different levels, you may want to place different decks of your deck plan at different heights. To make this easier, you can specify the same level number for all components of the deck plan that are to be set at the same level. Then, when you raise or lower any one component of a deck level, and do a Cleanup, all components of that level will automatically adjust as well. This allows for ease in editing. For example, if a joist depth were to be changed from say 9.5" to 11.875", all joists whose level number matched that of the one edited would also update their depth to 11.875".
You can change the level of particular items in one of the following ways:
· Edit individual component in the deck plan to the level desired. Note that:
- If the deck components have been drawn simultaneously or as a pre-combined deck unit, you must first explode (ctrl + e) the deck area
into its individual deck components before their levels can be changed.
· Select Draw ® Deck ® Level. Use the Level command to simultaneously change the level of a number of items.
For details on the Level command, see Specifying Levels for Joist Items.