Count me as another who has never heard it before now and assumed it would mean unadorned. In what way is a pikestaff obvious? Because they’d be hard to hide?
I’ve heard it often enough - mostly in books I read as a child.
Have you ever carried around a ten-foot pole? If you had, you wouldn’t even need to ask.
Living in a coastal fishing area in the NW of the US, I think the word pikestaff would refer to what we just call a pike. A long handle, usually made of aluminium now, with a metal point and a hook on the end.
The hook is used to catch the lines on floats for crab pots etc. and the point is used to guide floating debris or for docking. Pikes were also used to guide logs in the days when log rafts were common.
So is that what you mean by a pikestaff? Does the expression mean ‘plain as a pole?’
My Father used it, as did my maternal Grandmother.
Nothing to contribute to the debate but my ex once referred to something as being as plain as the pikestaff* on the end of your nose*.
I don’t remember when I first heard the expression, although it is vanishingly uncommon in the US. But, it was well before I read The Mote in God’s Eye, which is where I recall it’s use best.
Could the word “turnpike” be related?
Consider–
I know the phrase from English literature, but it’s very uncommon in the U.S. today. “Plain as the nose on your face” or “plain as can be” are more common here. When looking for something that should be immediately findable, a somewhat old-fashioned phrase I’ve heard more than once is, “If it were a snake, it would’ve bit you.”
I believe so: the traveller arrives at the toll-gate, pays the toll, and the gate-keeper turns the pike to allow the traveller onto the toll road. The gate is a pike.
I’m British and have never heard the expression before. Where I’m from, “as plain as day” is the dominant form.
Is this a whoosh? If not - who in the world brings a pike to a gun-fight? I mean, it’s better than a knife, I guess - but not by a whole lot.
I’m very surprised by these responses.
I’ve certainly heard the expression, and read it. I’m very familiar with it, and am amazed that so many Dopers aren’t.
It will now be a code phrase when Dopers get on Jeopardy.
We (Dopers) should make a resolution to restore the phrase to it’s former grandeur by adding it to our conversations today. 
“That’s fucking obvious” is the more common American phrase.
Observations of the painfully obvious may be followed by “No shit, Sherlock,” “Well, duh,” “Thank you, Captain Obvious” and “Ya think?!?!?!?!?”
That is not how “plain as a pikestaff” would normally be used, though. It is not for putting someone down for redundantly stating the obvious, it is for claiming that something is so obvious that to question it would be silly.
I’ve never heard “pikestaff,” but I have heard “day” and “the nose on your face.”
I also have a vague recollection of hearing “plain as plain can be.”
No whoosh.
The Confederacy was short on everything, except military officers.
And prior to the Civil War, & in some cases long afterward, militaries regarded the bayonet as the primary weapon, the bullet, secondary.
A military saying of the era:
Given a shortage of guns, the pike was seen as a good stopgap measure. To be abandoned the minute muskets were available.
Here is a link to a photo of a Confederate Pike head.
http://www.thetreasuredepot.com/cgi-bin/auction/auction_config.pl?noframes;read=516
Canadian. I’ve never heard or read the expression until this thread.
American, here. This is something I’ve read hundreds of times, but doubt I’ve ever actually heard. I’m surprised that it’s unfamiliar to so many. It’s something I might have chosen to say or write to give a sort of old-fashioned Englishy feel to things.