to stab (into); to thrust (violently)
to plant (in the ground, snow, etc.); to set; to stick (upright)
ナイフを地面に突き立てた。
I stabbed the knife into the ground.
旗を山頂の岩に突き立てている姿が見えた。
I saw someone planting a flag into the rock at the summit.
棒を砂浜に突き立てて目印にする。
I stick a pole into the sand as a marker.