Read the following passage:
The old mansion stood silent, its crumbling facade bearing the weight of countless tales yet untold. Vines snaked over the weathered stones, their green tendrils clasping tightly, as if trying to shield the secrets hidden inside. Every cracked window seemed to watch with a somber gaze, while the creaking door held its breath, anxious for the return of curious souls.
In this context, the word 'clasping' most closely suggests what about the tendrils of the vines?