We cut the 100mm strip in half so we now have 50mm x 50mm squares with still one strip of each side in the box we have enough to put up two pictures. If you're worried about it falling off there's no need as each piece at 100mm long is enough to hold up to 7kg in weight!
The technology behind the super strong fastener is the use of a double-coated rubber resin applied to the entire back surface of the tape, even when cutting you can feel just how sticky the glue is. The loop side of the tape is fairly standard, perhaps a little deeper than standard tapes whilst the hook side is the strip with all the magic, an all-plastic section with two-way facing hooks for superb strength both ways.
Once all 4 corners have a square of loop stuck on you can press the hook pieces to is with the glue side facing out, this way you can have all four corners ready with the hook and loop side together, take off the release paper from the hook side and press the whole board to the wall.
Before trying to level up your picture, let the glue dry over a 24-hour period. If you try to make adjustments to soon you will just peel the fastener from the wall.
One thing worth consideration is the size and weight of the picture, it might only need securing at the top, this would make adjustment much easier and your pack of Heavy Duty VELCRO would go even further!