In a D-ring strap, take the empty end through both loops and then fold it over itself. This empty end will now be on top of the rings. You should now take this non-ringed end through one D-ring to tighten the loop.   A cinch buckle has a divider which creates 3 sections/slots. Take the empty end of the yoga strap thread it from the inner section. Bringing the strap end over the divider, push the empty end into the outer section. You can loosen or tighten the loop using the empty end that you have pushed into the various slots.