When Trophy had blackmailed Knife and turned him into a slave, he had made Knife open any jars and lids he couldn't get open. Although after Knife had stopped being said servant, Trophy just ended up having meltdowns when he couldn't get the stupid jars open.

Which is why he was currently outside of Knifes room, whining and knocking on his door with a jar in his other hand, basically throwing a tantrum, "Knifeee!"