Remove the root end and green tops of the leeks with a sharp knife, leaving only the white and pale green section. Rinse thoroughly under running water to remove any mud or grit. Cut the leeks into 2" pieces. Skewer the leek pieces onto a bamboo skewer. For easier handling, cut each skewer in half with a pair of sharp kitchen scissors or garden shears. Brush with olive oil. Heat an electric grill, stovetop grill pan or outdoor grill and cook leeks until tender, turning to lightly brown on each side. Serve hot or cold.