To align, distribute, or resize a group of blocks:
Select the blocks that you want to align, as described in Select Multiple Objects.
Simulink® highlights one of the selected blocks. Simulink uses the highlighted block as the reference for aligning the other selected blocks. For example, in the following model, the Constant block is the alignment reference block.
One of the selected blocks displays empty selection handles. The model editor uses this block as the reference for aligning the other selected blocks. If you want another block to serve as the alignment reference, click that block.
From the Diagram > Arrange menu, select an alignment, distribution, or sizing option. For example, select Align Top to align the top edges of the selected blocks with the top edge of the reference block.