Mike the MMA* fighter and his fashion-model wife Wendy make a striking couple. They turn heads, especially when engaging in their favourite pastime - cosplay**.

Mike likes to dress as a fantasy hero, complete with sword and buckler while Wendy goes more for the delicate wood-elf look.

Whenever they have spare time from work, they go to their out of town workshop where they have tools, equipment and machinery to manufacture their incredible costumes. Depending on their schedules they may go together or separately.

When M goes alone to the workshop he always begins by operating machines*** LMD and RAD in that order. Before leaving for home, he always operates RAD; then he operates LMD and RAD in no particular order.

When W goes alone to the workshop, she also operates LMD then RAD in order. However she then operates both LMD and RAD again in no particular order. Before leaving for home, she operates LMD then RAD in that order and finally LMD and RAD in no particular order.

When they are there together, the order of things depends on who arrives/leaves first.


What are LMD and RAD and what do the letters stand for?
Why is the order sometimes important and sometimes not?
Why do Mike and Wendy operate LMD and RAD in different sequences?

I anticipate that the initials LMD and RAD will be the last thing to be discovered. They are there to prevent people from suggesting an alternative answer. However don't let that put you off, I guarantee that you are familiar with LMD and RAD, even if you don't know precisely how they work. Everything else but the initials can be solved with ordinary reasoning and ordinary knowledge. A final online search will give the meaning of the initials as it did for me.


I invented this puzzle. It's based on a real-life but less glamorous situation.

Although it may seem to involve logic, I haven't tagged it as such because probably every puzzle involves logic in some way and this one is based more on real-life knowledge and reasoning.


**cosplay - the activity or practice of dressing up as a character from a work of fiction (such as a comic book, video game, or television show) https://www.merriam-webster.com/dictionary/cosplay

*MMA - Mixed martial arts sometimes referred to as cage fighting, is a full-contact combat sport based on striking, grappling and ground fighting, incorporating techniques from various combat sports and martial arts from around the world. https://en.wikipedia.org/wiki/Mixed_martial_arts

***A machine (or mechanical device) is a mechanical structure that uses power to apply forces and control movement to perform an intended action. Machines can be driven by animals and people, by natural forces such as wind and water, and by chemical, thermal, or electrical power. https://en.wikipedia.org/wiki/Machine

  • $\begingroup$ You've explained what M and W do when they arrive, and before they leave. Do they operate LMD, RAD or other machines in between the set of things they do when they arrive and the set of things they do before they leave? Or have you described everything they do, exhaustively? $\endgroup$
    – Vicky
    Commented Feb 6, 2021 at 16:17
  • 1
    $\begingroup$ @Vicky - They do lots of other things in between and may use all sorts of equipment. They might operate LMD and/or RAD mid-session but then again, they might not. $\endgroup$ Commented Feb 6, 2021 at 19:49

1 Answer 1


A few thoughts which are too much for a comment but nowhere near an answer yet.

Given your careful definition of the word "Machine" this could include things like door handles, light switches etc.

[Now known to be irrelevant]

Wondering whether L.. and R.. mean Left and Right of something. If so, it's possible that M and W are right and left handed (respectively or vice versa). Or that might be coincidence.

[Now known to be irrelevant]

-I would expect the first things that someone does in a workshop (other than door handles and light switches etc) to be operating safety equipment, eg ensuring the guard is down or the blade is in the correct position.-

[Now known to be irrelevant]

-M and W may well be different sizes, so adjusting something such as seat position, table height etc.-

[Now known to be irrelevant]

The fantasy hero with sword and buckler would imply quite a lot of metal in the costume to my mind, whereas a wood elf would definitely not include metal. The one thing I can immediately think that they might have in common in their costumes is leather.

I am wondering whether the machines are part of a door handle / locking system. W wants to lock herself IN to the workshop for safety reasons, whereas M isn't fussed. They both have to lock it when they leave and unlock it when they arrive.

[So, my final answer:]

Aha, LMD is Lever Mortice Deadlock - this is basically a normal old-fashioned key operated lock where turning the key moves a bolt in the door in/out of a hole in the frame. The key can be removed from the lock whether the door is locked or unlocked. RAD is Rim Automatic Deadlock, where the key is used to unlock and open the door from outside and when the door is closed again the bolt shoots back into place. It has a little handle on the inside of the door which pulls the bolt out of the way so the door can be opened without the key from the inside, and usually a little "snib" or hook which locks the handle in place as well for extra security. Turning the key from the outside a second time gives an extra level of "lock".

When M or W arrive, they first use a key to operate the LMD. The door is now unbolted. They then use another key to operate the RAD and push the door open.

M then continues on his merry way making his cosplay stuff. Before he leaves, he uses the handle of the RAD to open the door, then pulls it closed behind him and turns the key in each of the LMD and RAD (in either order) to complete the locking sequence.

W on the other hand does not want unexpected visitors while she is wood-elf-ing herself, so once she has come into the workshop she pushes the snib on the RAD into place and turns the key in the LMD (again, in either order). Before she leaves, she must first unlock the LMD and then follow the same sequence that M followed when he left.

  • $\begingroup$ Your last guess is the correct one! Now all you have to do is explain the order that they operate them - sometimes in sequence, sometimes in no particular order. I think maybe the initials are too difficult. They are technical terms for this type of "machine". These "machines" work in a slightly different way from each other. $\endgroup$ Commented Feb 7, 2021 at 13:55
  • $\begingroup$ @chasly-supportsMonica is my final edit to this correct? :-) $\endgroup$
    – Vicky
    Commented Feb 10, 2021 at 11:06
  • $\begingroup$ Absolutely and completely 100% correct! $\endgroup$ Commented Feb 10, 2021 at 12:59
  • $\begingroup$ @chasly-supportsMonica Hooray, thank you! This was an enjoyable puzzle. $\endgroup$
    – Vicky
    Commented Feb 10, 2021 at 14:23

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