Possibly dumb question...
 

Does a bash guard replace the largest sprocket? Or is it simply designed as part of the crank?

No question is dumb . . . that's reserved for some answers ;).

Yes, generally the bash guard goes in place of the big ring. Depending on the type (esp. polycarbonate ones), it may necessitate longer chainring bolts. If you want to retain the big ring, there are still a handful of guards that bolt to the outside of the big ring. Salsa Tooth Fairy Triple is an example.

Is it possible to turn a triple crank into a single, by making the large ring a bash, using shorter bolts and simply deleting the small ring?

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Ed's shown a good example above. Know that deleting the small (granny) ring has nothing to do with bolt length on the big/middle ring position. A triple-ring crank has two sets of chainring bosses: the outer spider through-holes, which the big ring or bash guard mounts to on the outside; and the middle ring mounts to on the inside face. Then there is a smaller circle of blind holes to which the granny ring bolts. Chainring bolt length is going to be determined by the thickness of whatever is bolted to the outside (bash or ring) + spider + middle ring all sandwiched together.

If you are eliminating the granny and front derailleur, you will want something to keep the chain from dropping to the inside; so Ed's solution of the Blackguard inner plate bolted to the granny ring bosses is a good one.

Sweet, so I need 2 bash guards, One with mounting holes in a small enough diameter to fit into the granny mounting holes, and the other large enough to bolt where my large ring was...? Im pretty sure this isnt the most weight efficient solution, but it seems pretty darn cost-efficient. Thanks for the help!

There are some pretty lightweight - - and even more secure - - chain guide/bash combos that are worth considering too. Gamut G- or P-series come to mind.

Knew who took that before I even saw the watermark.