Click 
.
In the schedule area, click once on the left-most symbol attached to the horizontal bar. This will display the Selection menu.
Click the Size/Color tab.
In the Other Overrides section, 
Symbol is on top.
Designate that certain symbols are on top of other symbols. Normally symbols are drawn sequentially across a task, so that symbols on a later date will be on top of a symbol from an earlier date.
Customize a symbol to appear on top of other symbols:
Click .
In the schedule area, click once on the left-most symbol attached to the horizontal bar. This will display the Selection menu.
Click the Size/Color tab.
In the Other Overrides section, Symbol is on top.
Notes:
If two close symbols have been selected in this fashion, symbols will be drawn in date order.
