Something “built to scale” doesn’t literally mean “built to be scaled,” but there are jokes. “Prison walls are never built to scale” was posted on the website Pun of the Day in June 2002. “Prison walls are never built to scale.  (Pun of the Day)” was posted on the newsgroup alt.humor.puns on June 22, 2002.
   
   
Pun of the Day       
Great One Liners of the Month - June 2002
1. Prison walls are never built to scale.
 
Google Groups: novell.community.chat
hhhrrrmmmppppffffff
Felton
6/20/02
Be kind to your dentist because he has fillings too.
A skier retired because he was going downhill.
Prison walls are never built to scale.
 
Google Groups: alt.humor.puns
“Puns of the Weak” 06/21/02
Stan Kegel
6/22/02
(...)
Prison walls are never built to scale.  (Pun of the Day)
 
Twitter
Michael Klobe
@klobetime
Prison walls are never built to scale.
10:42 AM · Aug 14, 2008·Twitter Web Client
   
Twitter
Carazuul
@douglas_c_green
When asked why the model of the new jail didn’t match the finished building the architect replied: “Prison walls are never built to scale.”
3:34 PM · Oct 8, 2008·Twitter Web Client
     
Google Books
Two Nuns In A Bath
By Geoff Tibballs
London, UK: Constable & Robinson, Ltd
2009  
Pg. ?:
Why is it that prison walls are never built to scale?
 
Google Books
5,000 Great One Liners
Compiled by Grant Tucker
London, UK: Biteback Publishing
2012
Pg. ?:
Prison walls are never built to scale.
 
Twitter
sixthformpoet
@sixthformpoet
Prison walls are never built to scale.
7:00 AM · Jul 2, 2014·Twitter Web Client
   
Reddit—Oneliners
Posted by u/AceMatisse November 11, 2019
Prison walls are never built to scale.
COMMENTS
fmoss
Climbing walls, on the other hand, are built to scale.