Self Check-In
2 schools of thought - LH has self-check in with baggage in FRA among other locations. Huge bits of kit, but they scan and weigh the bag and spit out a tag if it's within limits (weight, number of pieces, dimensions, depending on the routing.
The other way is to check in via machine and use the quick drop-off. BA has that at LHR and NZ in AKL. Way to go