1) do they actually work?
2) how do you make your own?

1) Yes
2) Old inner tube and zip ties

or make a mucky nutz type thing

1) Yes
2) Old inner tube and zip ties

yup, very cheap, very effective

i used an old tyre with zip ties

Tiny mudguard, muckynuts style, is more effective than an innertube guard. Less ugly too. I’ve got one “proper” one and 2 I made myself out of random stiff plastic packaging materials, wouldn’t be without them now, they stay on the bikes all year.

^^ What Northwind said. Any old A4 plastic folder/envelope will make at least 2 or 3.

They work really well, I’ve got an innertube tye-wrapped between fork crown and brace, took a few minutes to do and cost almost nothing.

Had the inner tube deal on mine last year, this year I splashed out (sic) on one of the Crud Fast Fenders.

The inner tube actually looked better.

zip ties, old tube pair of scissors, five minutes effort and about an 85% reduction in crap in your face…

or pay £15 for a chopped up mouse mat from rapid racer if you want the factory/mug look….

This thread, might be of some help.
http://www.singletrackworld.com/forum/topic/mudguards-crud-catchers

If you make your own like I did, dont make them too close to your tyre.
If you’re making an innertube type one like the neoguards, you cant go far wrong.