a parcel tied with string
a ball/piece of string
In only two days, our relationship was like a strong string that [can] never be cut. (First Certificate in English; B2; Spanish)
guitar/violin strings
[T]he guitarist, who ha[d] just broken one string of his guitar, began to dr[i]nk some alcohol. (First Certificate in English; B2; French)
a string of questions
As a writer, she's enjoyed a string of successes.
Cities have grown, bringing with this growth a string of problems which were not thought of years ago. (Certificate of Proficiency in English; C2; Haitian Creole)
I may be able to pull a few strings, if you need the money urgently.
This isn't secret: I thought some of these ideas might be of interest and perhaps an article about them [i]n your newspaper would pull the necessary strings at the City Hall to produce some very much needed changes. (Certificate of Proficiency in English; C2; Catalan)
I'll drive you home - no strings attached.
It is not that often that one comes across true 'no strings attached' generosity. (Certificate of Proficiency in English; C2; Danish)