Engineering drawing abbreviations and symbols

slot drawing callout   Dan slot machine black knight

References bend information for flattened sheet metal drawing views For References the feature callout data from

It looks like it could be a hole and slot for alignment, but between the input and output seems like a bad place for those features T 8020 T-slot nut Extrusion Drawing Aluminium, dimensional, angle, white png Speech balloon Callout graphics, quote box, speech Balloon, callout png

liberty bell slot machine I am trying to grasp the concept of the round slot position callout I have to check part against the drawing where hole is datum B One for the slot center marks and one for the dimension callout 80% of all what I do ends up being sheet-metal with almost every bolt hole