I'm lucky enough to own some dumb bells, which I've had for a year or so. I have 10,15, 3 and 5 kg. I don't have the ones with plates, just solid dumb bells.
I've been putting the 10 and 15 I'd dumb bells together in each hand, by crossing one over the other, to equal 25 kg in each hand for dead lifts and squats. What can I do to increase the load on my muscles apart from more reps? If I put the smaller weights in a rucksack, would that work without affecting form?