This tool allows you to move to another block (or to the drawing layer). You must do this before you can modify entities contained within the block.
If you are already within a block and have not yet saved the changes you have made (using Block - Save from the menu) then the Save Current Block form appears first. You must decide whether to save or discard the changes before you can select another block.
Next, the Block Change form appears, allowing you to specify which block should be made current.
By changing block, you are changing the selection set. For example, entities which are selected in the block you are working on will not appear selected when you change to work in another block but will reappear as selected when you return to that block.
NOTE: The Block - Quick change tool or the Block Inspector on the Impact Explorer are usually much more convenient ways of changing block.
Related topics: Blocks, Block inspector