safe and sound
safe and out of danger

– examples:

Last Monday the children disappeared. The parents were relieved when, on Tuesday morning, they were found safe and sound, hiding in an old cottage.

“Don’t worry about the money, it’s locked safe and sound at the office.”

safe pair of hands
a reliable person who won’t allow something to fail

– examples

After the disaster of the last management team, everyone was relieved to see that the new manager brought a safe pair of hands and a cool head.

“Don’t worry, your children are in safe hands. You’ll see them in an hour.”

safety in numbers
a big group is safer than doing something by yourself

– examples

“We’ll travel together, OK? There is safety in numbers; I don’t think any tigers will try to attack all of us if we stay to together.”

salt in the wound
(usually ‘pour salt in the wound’ or ‘rub salt in the wound’)
to do something to make a painful or bad situation feel even worse; ‘add insult to injury’

– examples

“It was bad enough when Anna said she was leaving me and taking the kids, but her taking the dog too was just rubbing salt in the wound.”

salt of the earth
(adj.) used to describe a person who is ‘down to earth’, dependable, kind to others, and not pretentious

– examples

“I like Dave: he is a good, honest, salt of the earth type of guy. Tells you the truth, and always tries to help you out.”

same old, same old
(usually spoken)
the same as always

– examples

There is a new boss, but in terms of losing money it is just the same old, same old.

“How’s it going?”
“Same old, same old.”

save face
to do something to keep a person’s reputation; to try not to embarrass yourself (or someone)

– examples

“This whole weekend has been a disaster. I think the best I can do now is just try to save face and hope they forget who I am.”

save (someone's) bacon
to save someone from a bad situation

– examples

“Thanks for telling my wife I was with you last night; you really saved my bacon there.”

saved by the bell
to be saved from a difficult situation because time finishes, or something else needs done

– examples

“I thought they were going to beat me up, but then one of their phones rang and they all had to leave. Talk about being saved by the bell.”

saving grace
the good thing that makes up for all their bad qualities; the good thing that counters their bad qualities

– examples

Dave is an idiot at weddings. He talks too much, drinks too much, and tries to flirt with the bridesmaids. His only saving grace is that people tend to find him funny. [/

(you) scratch (my) back, and (I'll) scratch (yours)
if you help me, I’ll help you

– examples

“I know you want me to help you, but I don’t work for free. Let’s just say, if you scratch my back, I’ll scratch yours: I need someone to look after the children this Saturday.”

a steal
A bargain. Got for far less money than it could have been bought for.

– examples

Davids has been a steal: bought for only 1 million, he has scored in every game for them this season.

At only $500, this car is a steal.