Techniques for tracking a location of an item retainer are described. In an example, a computer system may receive one or more signals from one or more devices. At least one device may be located at a distance from a radio frequency identification (RFID) reader. The RFID reader may be located at a space opening and may cover a read zone around the space opening. The signal(s) may indicate that a condition to activate the RFID reader is met. This condition may be associated with a state of the space opening or a proximity of an item retainer to the read zone. The computer system may activate the RFID reader based on the condition being met and may determine a progress of the item retainer through the space opening based on whether an RFID tag was read by the RFID reader while the RFID reader was activated.