+ (yī一) + reduplicated verb
Stating how one anticipates the object will be dealt with.
Completed action uses –le了 instead of yī一. The sentence may need to take a clause.
Qǐng bǎ zhèi kài biǎo xiūxiu. 请把这块表修修。(same in meaning as + yī一 + reduplicated verb) Please fix this watch.
Qǐng bǎ zhèi kài biǎo xiū yi xiū. 请把这块表修一修。(same in meaning as + reduplicated verb) Please fix this watch.
Tā bǎ zhèi kài biǎo xiū-le xiū, xiànzài yòu néng zǒu le. 她把这块表修了修, 现在又能走了。(-le了 + verb) She fixed the watch a little bit and now it's working again.
Note: Monosyllabic verbs when reduplicated can take yī一 or le了 inbetween, as in 9.2 and 9.3. Disyllabic verbs when reduplicated may not do the same. So it would be wrong to say jiěshì yi jiěshì解释一解释 'explain' or jiěshì le jiěshì解释了解释.