Automated storage and retrieval system comprising a transfer column with side opening with blocker and method of operating blocker

A method of transferring a goods holder through a side opening in a transfer column in an automated storage and retrieval system, the automated storage and retrieval system comprising a two-dimensional rail system comprising a first set of parallel rails arranged to guide movement of container handling vehicles in a first direction across the top of a framework structure, and a second set of parallel rails arranged perpendicular to the first set of rails to guide movement of the container handling vehicles in a second direction across the top of the framework structure which is perpendicular to the first direction, wherein a number of container handling vehicles operate on the rail system for storing and retrieving goods holders in the automated storage and retrieval system, and wherein the framework structure comprises a transfer column comprising a side opening and an adjustable blocker for obstructing the side opening (60), the blocker comprising a guiding surface for guiding a lifting device of the container handling vehicle vertically past the side opening;

• and wherein the method comprises:
• moving the blocker from a first position to a second position, where, in the first position the guiding surface is positioned to guide the lifting device vertically in the transfer column and obstruct horizontal movement of a goods holder through the side opening, and, in the second position, the guiding surface no longer guides the lifting device and allow horizontal movement of a goods holder through the side opening.