Purchased an older home with odd custom kitchen cabinets. I am wanting to remove the ugly box range vent and add a box shelf and an OTR microwave, but the width between my side cabinets is 28 inches. How big of a problem is it to move these cabinets over to increase the width.
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Picture(s) would help for your "move these cabinets over" statement. But, if you have room then it's just unscrew from each other & from studs...in that order. To then re-mount them to other studs & back to each other.
However, you may also be able to swap cabinets to get a few more inches. If you have cabinets on other walls there may be a thinner one in an area that can accept the fatter one.