[Mystery all-brass slide rule. What was it used for?]

That is a millwright tool used in motor alignments and hole depth checker and many other things you can do with it 

[DeWalt 20v Mower]

Hey fellas I just bought the mower and my grass had gotten out of hand and it was a little taller than it needed to be and my mower bogged and when I released the handle the motor wouldn't ever re-engage even tho the lights light up like it's about to engage it just doesn't and tips?

[Dewalt electric mower]

I bought a new dewalt mower and the grass had gotten out of hand and it bogged down and turned off and the motor will not re-engage although the battery light light up as it is was about to engage it jist never does

I tried the reset button on the side where the handle pushes it in when you fold it up and it wasn't stuck in the wrong position