Givi E21 panniers, I drilled a couple of mounting holes in them and now want to fill them back in. what scrap plastic can I use? I seem to remember ABS guttering is the same as fairing panels. can I use this?
I’d use silicone or an epoxy. What did you plan to do with the guttering?
Melt LEGO bricks 
Sugru?
I don’t imagine panniers are made of ABS - probably polypropylene, I’m pretty sure that’s what my topbox is.
Perhaps a nut, bolt and washer arrangement might be more secure than trying to plastic weld, if there is the space.
Or maybe a rivet?
You can melt some ABS plastic in acetone and fill the gap- it might make its way loose though.
Another way is to use a plug cutter that creates a conical wedge that you can glue into place and then trim with a flush cut saw.
I do it all the time with wood- cutting a plug of ABS plastic is probably just the same.
How large is the hole?
If under 3mm or so then I’d probably just fill it with some silicone, as Avi suggests.
Stop doing Heath Robinson mods on your bikes and accessories?
I repaired the golf ball size hole in my Givi E21’s with a ‘Big Boy fibre glass repair kit’
two layers inside, one layer outside and a coat of matt black from a rattle can for a perfect repair.
IF the guttering was the same plastic I was going to melt it down. holes are 6mm.
This stuff
Or if going the Lego brick route grate a black lego brick into acetone (nail varnish remover) once melted you can apply it and shape it by hand its pretty much like putty
I’ve never really trusted the molten-plastic (either with heat or acetone) but I’ve also not tried it properly. Epoxy and fibreglass are so easy to get hold of and since they’re actually made for doing this sort of thing it’s probably easier to get it right with them.
Keep yer fingers off that drill in future MeG.
And if you’re melting drainpipes - make sure you have ABS, not PVC. The fumes from melting PVC can be pretty nasty.
Something else worth trying is this:
http://ecx.images-amazon.com/images/I/41-z2SurX2L.jpg
I use it for attaching plastic binding to guitars.
It will weld most types of plastic to other types of plastic and other things (like wood).
+1 Sugru
I’ve melted cable ties with a soldering iron into broken fairing panels with some success.
Other than that, JB weld.