The Same X tool 
and the Same Y tool
enable you to align selected points either horizontally
or vertically relative to another point.
First, select one or more points.
Then, select a point that will define the position of all the points.
Finally, select the Same X tool or the Same Y tool.
If none of the points are constrained, the points that you select first will move to be aligned with the point that you select last.
If points are constrained, whenever possible, the independent points will move to be aligned with the constrained point.
Note: If the original point is not in the current sketch, you must add it to the sketch as a reference entity.
To align one or more points either horizontally or vertically with another point:
Select the
Add Constraints 
icon from
the Sketcher toolbar.
The cursor will be a pointer-and-grid 
symbol.
Click one or more points that you wish to align.
Click the point to which the points selected in step 2 will be either horizontally or vertically aligned.
Click the Same
X tool or the Same
Y tool on the Constraint toolbar.
The points(s) selected first (in step 2) are now either horizontally or vertically aligned to the point selected last (in step 3).
In the example above, none of the points are constrained. If points are constrained, whenever possible, the independent points will move to be aligned with the constrained point.
Notes:
You can also first pick the entities to constrain (while in Select mode), then select the Add Constraints option, then choose the desired constraint.