I buy full sacks of grain, and over the past 10 years it's always been hit and miss getting that string that ties the bag close to unwind. If you get it just right the string unwinds with a gentle pull. If you get it wrong its a big PITA having to cut through each knot. Any pictures or videos on how to do this repeatedly?
In my experience it can differ between maltsters, but Weyermann offers both PDF and video instructions on opening their bags (the video is pretty awesome), which are fairly applicable to other brands of malt.
There's also this video.
My own personal method for this, which I find works pretty much 100% of the time, with any bag:
First, be facing the correct side of the bag. This one:
Not this one:
Pull the tail away from the bag a bit to expose the stitching; take those first two blue stitches on the far left of the bag, and cut them, between the bag and the rest of the 'tail' (see red mark below). Note that strings may be a different color, but will be in the same place:
The resulting tail should pull right off: