How can I stop slate chippings going down drain?

[Savik2]

I'm intending to lay some slate chippings in the sunless area around my back door, because the concrete there is badly cracked and covered in slippery algae. Trouble is, the area is like a sunken pit, and slopes towards a rainwater drain - the little square kind with a grating. The slate chippings are therefore quite likely to drop into the drain! Is there anything I can buy to stop it happening? I'm thinking of a raised grating of some sort, but Googling the term doesn't reveal anything useful. Perhaps I'm not using the right terminology.... Can anyone help?

[Clanad]

If the openings on the grate aren't too large one could almost fill the drain pit with largish gravel... at least 2 inches in diameter. Then fill the last few inches with the slate ships. I've built a pondless water fall that way here in the U.S. Point is to fill the area around the drain with large enough stones so they don't wash down and they will become a base for youe decorative chips...

[ruthann58]

i have got a piece of small mesh wire netting over mine as i have the same problem a near my back door

[Savik2]

Thanks for the input - and duh... Both ideas are so simple, I feel a right nit-wit for not thinking of them myself! What's even more daft is that I have both materials close at hand. Good thing I've got enough smarts to consult Answerbank, though - I can confidently predict I'll be posting many more idiotic questions as my garden make-over progresses!