Blender 3D
View
Fit view to object: Numpad .
Show/Hide Objects
Source
Hide selected objects: h
Hide unselected objects of the scene: Shift-h
Show hidden objects: Alt-h
Object
Set object origin point (center by default)
Source
Set “cursor” to object corner, than click “Object -> Set Origin -> Origin to 3D Cursor”.
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Set object size (dimentions)
Open “Properties” panel (press n key).
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Scene
Set grid size to millimeters
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Set units to millimeters
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Panel
Toggle “Properties” panel: n