When it comes to turnout controls, one of the questions that has impeded progress is whether or not they should be locked. There were really two questions at play: are switches in yards locked, and if so, when did the practice start? Secretly, I was hoping that like headlights in daytime, this was one of those differences enjoyed by us modellers of earlier railways.
The answer to the first question is an emphatic “yes.” Certainly, main tracks within yards are locked. Side tracks may only have a hook through the switch stand that keeps it from shifting accidentally.
The second question was harder to resolve. The only mention I can find of locking switches even in contemporary rule books state that switches must be locked if locks are provided. The American Railroad and Maintenance of Way Association has some likely-looking resources, but they are behind a steep paywall.
So, I turned to the wisdom of my friends. I am thankful to Len Thompson who passed my question on to railway historian, Doug Phillips. Doug worked in engineering for the CPR, and his response was so authoritative, I am inclined to take it as truth. He indicated that main tracks on Canadian railways were locked as early as the 1880’s (US roads were later).
The other interesting item discovered in this particular rabbit hole is that switches are normal when the handle is thrown to the left. That is worth remembering as it will make it easy to check if all the switches have been set to normal by simply looking along the fascia. I also learned that the handle should be positioned toward the points so that the operator can see what they’re doing.
Photo Credit: Joseph Bishop, http://www.railpictures.ca/
Pembroke:87 
Rene – I look forward to seeing your working HO scale switch locks………….
They’ll be ready right as soon as your working HO scale fingers to operate them. 😀