An NBC news analyst, reporting on the U.S. Presidential election last night:
We need to look at our toolbook — I mean our toolbox, our playbook…
A blend of two (somewhat) idiomatic compounds, conveniently identified for us in the speaker’s own correction.
Note that the contributors to the blend are very similar in structure: both are N + N compounds, both Ns are monosyllables, and box and book are already very similar phonologically. General principle:
The greater the degree of morphological and phonological similarity, the more likely semantically similar items are to interfere with one another in blends.
Related blends: pitchfork from pitch pipe + tuning fork (from a musician); rocket surgery from rocket science + brain surgery (dismissively, in contexts like It’s not ___); jerry-rigged from jerry-built + jury-rigged; heart-wrenching from heart-breaking + gut-wrenching; Achilles’ tooth from Achilles’ heel + sweet tooth.
And note that toolbook also exists as a deliberate portmanteau, presumably of toolbox and handbook:
ToolBook is a Microsoft Windows programming environment, released in 1990 by Asymetrix Corporation (later known as click2learn and SumTotal Systems). In that day ToolBook was a competitor to Visual Basic as a programming environment. Over the years ToolBook has been enhanced to allow for the creation of web-based (HTML) content as well. (link)