Opening a letter
At the very beginning of the novel, the author describes the uncertainty of opening a letter, using strong imagery: "You can open an envelope and take out something which bits or stings, though it isn't a living creature." Here, Keun is referring to the fact that letters can hold good or bad news, and that there is no way of knowing which one it is going to be. As this novel is set during a war, the chance of the news being something bad increases dramatically, heightening this sense of uncertainty and fear.
Gerti imagery
Gerti is described as having provoked "an SA man... saying the soldiers of the Regular Army have nice uniforms and are better looking too." Her comments are described as acting on the soldier "like a swarm of angry hornets, stinging him badly." As such, imagery is used here to emphasize the offense Gerti has caused.
