I got the idea of doing it while taking a shower in the morning. 3 years ago when we had a prolonged rain event, water leaked through the vents into my crawlspace. That's not nearly the worst that can happen (and I had some attic leaks too), but I like my crawlspace to stay dry.

I scooped my leftover wet mortar into 2 small aluminum pans, to make some stone blocks. I got that idea from a YouTube video where they were using mortar to make decorative paving blocks.