You can use the object snapping feature while placing store racks, warehouse racks, decorations, cash registers, speakers, and fitting rooms.
(You can disable it in the Options - Gameplay settings.)
If you want to use the object snapping feature on wall racks, you should know that they are only functional with other wall racks.
Align Snapping Objects
If you "Hold Left Shift (by default)" while placing an object, you can align the object.
(It's Left Shift by default, but you can change it in the Options-Controls.)
If you don't want to use the object snapping feature, you can disable it in the Options - Gameplay settings.