We have some new neighbours that have moved in next door and they ask to
borrow garden tools (and car tools).

The problem for me is I have to go and ask for them back, and they are not
always there. I wanted to use my garden rake today and went around to get it
back, but they are out; so I cannot do the job.

We like these neighbours and want to remain friends. What reason can I give
to them not to lend my tools to them which will cause the minimal amount of
friction? I'm looking for an imaginative (yet plausible) excuse to give
them.