Am I going to have to

The huge transfer involving Lincoln refers to Waterfall; it isn't very well worded.
 
The club has tweeted this morning :

<blockquote class="twitter-tweet"><p lang="en" dir="ltr">? <a href="https://twitter.com/hashtag/OnThisDay?src=hash&amp;ref_src=twsrc^tfw">#OnThisDay</a> 2004<a href="https://twitter.com/G23mcauley?ref_src=twsrc^tfw">@G23mcauley</a> made his debut for the Imps in a 1-0 victory at <a href="https://twitter.com/shrewsweb?ref_src=twsrc^tfw">@shrewsweb</a>.<br><br>The rest? History. <a href="https://twitter.com/hashtag/ImpsAsOne?src=hash&amp;ref_src=twsrc^tfw">#ImpsAsOne</a> <a href="https://t.co/vtFlWTWP8y">pic.twitter.com/vtFlWTWP8y</a></p>&mdash; Lincoln City FC (@LincolnCity_FC) <a href=" ">August 7, 2018</a></blockquote> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
 
https://www.efl.com/-more/governance/efl-rules--regulations/section-6---players/

43
Registration of Players
...
43.2
Subject always to the provisions of Regulation 43.3, after the expiry of each Transfer Window (and/or in the Extended Period, if applicable) in each Season registrations of Players and transfers of registrations will, except as permitted in Regulation 55, be declined or will only be approved:
...
43.2.2
where the Player is an Out of Registration Player;


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any 'out of registration' player can still be signed outside the window, although there might not be many good apples left to choose from.