This Christmas MrsT gave me a 12v Bosch Professional cordless circular saw. Bosch, wily buggers that they are, sold it unbundled, with battery and charger not included, and I ended up with the right charger and the wrong battery. Ultimate insult, the battery fits the charger but not the device, so I ended up buying the right one myself.
Nar then: the batteries look almost identical, but one is from Bosch's 'hobby' range (green) and the other is from the 'pro' range (blue). The hobby one is rated 12v 2.5 ah and the pro one 12v 2.0 ah. The only visible difference is in the lugs that hold the battery in the device: on the hobby battery they're squarish and on the pro they're squarish minus a corner. I could Dremel off a corner from the hobby one and it would fit.
Question: why shouldn't I?