60 inch/pounds refers to 60 lbs. of pressure exerted on a wrench with an inch-long handle, or one pound of force exerted on a tool with a 60" (5') handle.

Playing with these numbers, you can see how a tool with a one-foot handle would exert 60 inch/pounds if you put 5 lbs. of force on the handle. Heft a 5 lb. household item (e.g, a bag of flour or sugar) in your hand and see what it feels like. Try to replicate that amount of force on your ratchet handle (a little more force for a typical 8" handle) and you'll be close enough. The handle should stop rotating when you have applied this amount of pressure or you'll be exceeding the desired torque.

Unless a torque wrench is brand-new, undamaged, and perfectly calibrated, it won't be spot-on either. I own a couple of torque wrenches, but there is sometimes insufficient clearance to use them, so you learn to make reasonable guesstimations.