An injection device and an injection device trainer for training a user to use an injection device. Each one of the injection device and the injection device trainer can include: a body portion； an actuator positioned towards a proximal end of the body portion, the actuator moveable from a proximal position to a distal position； a shield positioned towards a distal end of the body portion, the shield moveable between: an initial position； a retracted position that is more proximal relative to the body portion than the initial position； and an extended position that is more distal relative to the body portion than the initial position； and a locking member rotatable between a first orientation in which the locking member resists movement of the actuator from the proximal position to the distal position； and a second orientation in which the locking member permits the actuator to move from the proximal position to the distal position.一種注射裝置及一種用於訓練一使用者使用一注射裝置之注射裝置訓練器。該注射裝置及該注射裝置訓練器之各者可包括：一本體部分；一致動器，其經定位成朝向該本體部分之一近端端部，該致動器可從一近端位置移動至一遠端位置；一護罩，其經定位成朝向該本體部分之一遠端端部，該護罩可在一初始位置、一縮回位置與一延伸位置之間移動，該縮回位置比該初始位置相對於該本體部分更近；該延伸位置比該初始位置相對於該本體部分更遠；及一鎖定構件，其可在一第一定向與一第二定向之間旋轉，在該第一定向中，該鎖定構件抵抗該致動器從該近端位置移動至該遠端位置；在該第二定向中，該鎖定構件允許該致動器從該近端位置移動至該遠端位置。
