<munderover> stretch width

This test passes if you see the black thing has the same width as the red bar.

\overset{↜}{}

This test passes if you see the black thing has the same width as the red bar.

\underset{↜}{}

This test passes if you see the black thing has the same width as the red bar below and wider than the green bar above.

\overset{\overset{}{↜}}{}

This test passes if you see the black thing has the same width as the red bar below and narrower than the green bar above.

\overset{\overset{}{↜}}{}

This test passes if you see all three things have the same width.

\overset{↜}{\underset{↜}{}}

This test passes if you see the black thing has the same width as the red bar.

\underset{\underset{}{\underset{}{↜}}}{}

This test passes if you see the black thing has the same width as the red bar.

\underset{\frac{\frac{↜}{}}{}}{}

This test passes if you see the black thing has the same width as the red bar.

_{↜}^{}

This test passes if you see both the red and blue things have the same width as the black bar.

\overset{\underset{}{↜}}{↜}