did a search for this but couldn't find anything that answered my questions...

just got my first set of crampons (grivel g12) which i am trying to fit to my boots (new model scarpa manta size 45). unfortunately i didn't have my boots with me when i bought them, but the shop said they're a good fit.

i just can't work out how big/small they should be! the heel sits nicely at the back, can't really adjust that anyway. but how long should i make them? where should the front/side points come to? how tight should they be?

hope someone can help me...

Basically they should be as tight a fit as possible without distorting the boot. To do this effectively you need rigid boots or attach the crampons with your boots on. The sole of the boot should be pressing against the crampon both front and back.

Imagine the front and back of the crampon "cage" as a clamp - like Dave says you'll need to apply some weight if there's much flexibility in the soles (so don't try it on the kitchen lino)

There shouldn't be any overhangs laterally either, ie the sole should cover the points.

I still use the old trick of picking up a boot with crampon fitted but the straps undone, holding it upside down by the central crampon bar and then shaking it. If it stays on and doesn't move it should fit okay.