After adding your sets to Rebrickable, you can use the Build function to see what other models you can build. However, by default, the Build function uses all the parts of the sets you have added. Suppose you have one or more sets on display, and you really don't want to take them apart. That's when you need Assembled Sets.
This feature is designed to allow you to mark parts as currently assembled in a Set or MOC and are not to be counted in Build calculations - without having to actually remove those parts from your buildable collection. Great for when you don't really want to take this Set/MOC apart to build something else. No actual changes will be made to your LEGO Collection. This only affects the Build calculations.
To show your Assembled Sets: select your Profile and then select Assembled Sets.
The Assembled Sets page contains a standard set list with sort options (Year, Name, Number of Parts, Set Number), Drill Downs and a counter line. If you don't have any Assembled Sets, you'll see a information box with the following text "You have 0 sets which are being subtracted from your buildable parts in Build calculations."
To add a set to your Assembled Sets, search the set and select the image to open the Set Details page. Scroll down until you see the list of Add buttons, and press thebutton. The Mark Set as Build/Assembled dialog will open and show how many parts will be marked un-usable. Press the button to confirm.
If you try to add the same twice, the following error message will be displayed: "You already have this set Built. See your list of Assembled Sets."
If you try to add a set you do not own, the following warning will be displayed: "Warning - Missing Parts. You are missing xxx parts from this Set. This feature is meant for use only when you have 100% of the parts in your LEGO Collection. It will still work, but probably means you do not have an accurate collection stored in Rebrickable."
To delete a set from your Assembled Sets, first select the overview page and then press the delete button below the set image. Be careful, there is no delete confirmation, the set will be removed immediately.