Perhaps Albus was hoping to dodge the question once he had started the journey, for he winces before quickening his pace. "Because there are body parts that render such a rune more efficient - or ineffective," he replies impatiently, striding out a little faster. "Runemasters know that a network of energy flows through a human body, and the nodes give the best results with triggerable runes. I didn't want them to have to be imprinted again." Turning to Harry, his lips curl into a broad, not particularly happy grin. "It's certainly not pleasant, I can assure you."