The symbolic representation of this rune is a shelter from the destructive force of natures hailstorm. It is fairly easy to envision the cross-bar stave between the two upright staves providing the shelter under which safety from the storm could be found
The concepts that surround Hagalaz recognize that the destructive potential for hail out of season is balanced by the potential for transformation that will bring new fertility and growth.
It can be seen as representative of the cosmic "egg", the primal layered egg of ice that was transformed in combination with fire. Out of the primal chaos (which we think of as destructive) comes a tangible force that carries the potential for transformation. The transformation from destruction to fertility comes after "being tossed by the winds".
Hagal represents a dramatic event or trauma which comes from outside your own immediate perceptions. It represents a deep reshaping. The rune is deeply integrated into the mysteries of renewal through destruction, the shaman who, like Odin, loses all in order to find his or her own personal power.
It can also find use in defensive magic both by invoking the protection inherent in Hagal for yourself, and also for calling down the destructive power of Hagal upon enemies less prepared to withstand the storm than yourself. Of course, to be successful in this, you should be pretty sure that you are more prepared for the destruction of the storm than your rival.
As it is my rune, in my own personal version, I'd like it to be a tribute to my beloved KEITOLOGY :*