Capping couplet is one rhymed couplet of two lines, which have the same metre. These are typically found at the end of poems or at the end of a stanza in a poem and in plays at the end of a speech or scene. Capping couplets, too, fall under the nomenclature blank verse or iambic pentameter.
Shakespeare frequently used capping couplets in his plays as well as his sonnets. These lines from Romeo and Juliet, is an example of a Shakespearean sonnet, although as lines shared between Romeo and Juliet.
ROMEO
If I profane with my unworthiest hand
This holy shrine, the gentle fine is this:
My lips, two blushing pilgrims, ready stand
To smooth that rough touch with a tender kiss.
JULIET
Good pilgrim, you do wrong your hand too much,
Which mannerly devotion shows in this;
For saints have hands that pilgrims' hands do touch,
And palm to palm is holy palmers' kiss.
ROMEO
Have not saints lips, and holy palmers too?
JULIET
Ay, pilgrim, lips that they must use in prayer.
ROMEO
O, then, dear saint, let lips do what hands do;
They pray, grant thou, lest faith turn to despair.
JULIET
Saints do not move, though grant for prayers' sake.
ROMEO
Then move not, while my prayer's effect I take. (I.v.85-98)The last two rhyming lines in blank verse, caps the speech, signalling a sonnet within the play. A Shakespearean sonnet is in fourteen lines which ends with a capping couplet such as this, where, incidentally, Romeo caps his speech with a kiss.
[...]
Therefore let our proportions for these wars
Be soon collected and all things thought upon
That may with reasonable swiftness add
More feathers to our wings; for, God before,
We'll chide this Dauphin at his father's door.
Therefore let every man now task his thought,
That this fair action may on foot be brought. (I.ii.305-311)In Henry V, Shakespeare ends scene ii of the first act with Henry's capping couplet. The capping couplet is used by other poets and playwrights including Sir Philip Sydney, Edmund Spenser, Lady Mary Worth and Michael Drayton.
FUN FACT: Although, called a Shakespearean sonnet, this style of sonnet is not invented by Shakespeare but perfected and popularised by Shakespeare. This style is also referred to as Elizabethan sonnets or English sonnets.