Here are two excerpt from the WT I wrote for myself:
By setting the oval red gates alternately open and closed and watching the two patrol drones as they move, you can get both of them in the section of ductwork above the upper gate and then confine them there, thus giving yourself a safe path to the immobile maintenance robot. When you have done this the upper gate will be red and the other three blue.
Now you have to go to the immobile maintenace robot and get the robotic hand--the robotool.
Use a ring to get the map and ductwork overlay again. Release the drones from the upper ductwork section and manipulate the ovals to allow them into the section on the right of the right oval, which is then made red to confine them there, and make the other three blue. You have just been in this duct where the drones are now trapped, and you do not need to go there again. Return into the ventilator duct and go straight up to where the drones were previously trapped. At the end of the duct you will find a grate that can be removed by using the robotic hand on two screws at the top corners of the grate. Click on a grate handle to remove it.