a beam, abeam

A beam or a beam ( two words ) means one ( a ) square piece of wood or metal, used in construction ( beam ) --
He was knocked off the building by a beam the workers were moving.
You'll need a beam the right size to replace this one.

A beam may also mean one ( a ) ray or shaft, as of light ( beam ) --
A beam of light comes through the shade, very early in the morning.
The cat will chase a beam of light for hours.

Abeam or abeam ( one word ) means at a right angle to the length of a ship or plane --
There is a ship abeam of us, but I can't identify it.
The ship was abeam of the dock, and couldn't get closer.

Now that you know that, you can say--
"The ship lay abeam of us, flashing a beam of light to signal for help."

repinned, repined

Repinned or repinned is the past tense ( yesterday, or some time ago ) of "repin", meaning to fasten or attach, again, with a thin sharp piece of metal, or the figurative equivalent --
The pattern came loose, so I repinned it.
She repinned one of the recipes that I shared.

Repined or repined is the past tense ( yesterday, or some time ago ) of "repine", meaning to mope or to be dejected --
He repined at the loss of his Summer romance.
It was useless, but he repined over the verdict for weeks.

Now that you know that, you can say--
"He sat and repinned the ribbon to all of her old letters, and repined at the loss of his youth."

failure, fail your

Failure or failure ( one word ) means defeat or a lack of success; a malfunction or defeat, or the neglect of an obligation --
He started his own business, but it was a failure.
They blamed their failure on poor coaching.
His failure to comply with the regulations led to his dismissal.

Fail your or fail your ( two words, rhymes with failure ) means to be unsuccessful or inadequate ( fail ) followed by "your" --
You will fail your exam if you don't study.
The teacher will fail your paper if you hand it in late.

Now that you know that, you can say--
"Your failure last semester doesn't mean that you'll fail your finals this term."

shell, she'll

Shell or shell means a hard outer case of some kind --
The turtle won't come out of its shell.
I got a bit of egg shell in the batter.

She'll or she'll is a contraction ( short, informal form) of "she will" --
"She'll be driving six white horses when she comes..."
When she gets home she'll be glad to see you.

Now that you know that, you can say --
"Ask Grandma if she'll help you look for a shell to put on your sandcastle."

often, oft in

Often or often ( one word ) means frequently, or on many occasions --
Is he often this grouchy?
It's our favorite restaurant; we go there often.

Oft in or oft in ( two words ) is an old-fashioned or poetic term meaning frequently ( oft ) [ followed by in ] --
"Oft, in the stilly night..."
The bard is oft in love; it fuels his poesy.

Now that you know that, you can say--
"The students were oft in high spirits, and even more often in trouble."

be head, behead

Be head or be head ( two words ) means [ be ] the chief  or superior ( head ) --
He wants to be head waiter, but he doesn't have enough experience.
He may be head of production when the current head retires.

Behead or behead ( one word ) means to decapitate, to cut off the head --
The French used the guillotine to behead people who were condemned to death.
The British Parliament voted to behead their king, after trying him for treason.

Now that you know that, you can say--
"Who will be head of state after we behead the king?"

forbear, for bear, forebear

Forbear or forbear ( one word ) means to refrain from doing something; to resist the urge to do something or say something --
It took all of her self-control to forbear kicking him.
Try to forbear blurting out the obvious retort.

Forebear or forebear ( one word ) means an ancestor, or a relative of some kind from the past --
He bore a close resemblance to his forebear, the man in the old portrait.
He was given the name of an illustrious forebear, but it was an embarrassment to him.

For bear or for bear ( two words ) means [ for ] a large hairy animal that can walk on its hind legs ( bear ) --
They will hunt for bear on their next camping trip.
He stormed out of the office, loaded for bear.

Now that you know that, you can say--
"He had to forbear shooting at the deer; he was determined to hunt for bear, as his forebear had done centuries ago."