Importing single symbols in the sense of “How does the assignment work?”

Question

I looked at Importing a Single Symbol From a Different Font and Handwritten R-like-kay. As a result, I downloaded the STIX package and looked up the highly welcome curly k \kay and found it to have the "coordinates" stix-mathscr (on page 37 of the newest documentation v1.1.1-latex from 2014/07/3); they are:

15x, ''6x  '3

What does this signify and how can I use it to import it? I guess the actual code would be similar to the answer in Importing a Single Symbol From a Different Font. Sorry, if the question is a bit redundant, but I think for non-experts the whole symbol importing business is pretty hard to understand.

Answer 1

Method 1 (Recommended by egreg)

Thanks to egreg for providing a way to save a maths alphabet which even works with \boldmath:

\documentclass{article}
\usepackage{amsmath}
\DeclareFontEncoding{LS1}{}{}
\DeclareFontSubstitution{LS1}{stix}{m}{n}
\newcommand*\kay{%
  \text{%
  \fontencoding{LS1}%
  \fontfamily{stixscr}%
  \fontseries{\textmathversion}%
  \fontshape{n}%
  \selectfont\symbol{"6B}}}
\makeatletter
  % the current math version is saved in \math@version
  \newcommand*\textmathversion{\csname textmv@\math@version\endcsname}
  \newcommand*\textmv@normal{m}
  \newcommand*\textmv@bold{b}
\makeatother
\begin{document}
  $\kay$ {\boldmath$\kay$}
\end{document}

Method 2 (initial solution)

This is extravagant in terms of its use of maths alphabets since it wastes one for a single symbol. However, I'm leaving it here in case you can spare the alphabet. If you wanted to use multiple symbols from the same font, this would be the way to go.

\documentclass{article}
\DeclareFontEncoding{LS1}{}{}
\DeclareFontSubstitution{LS1}{stix}{m}{n}
\DeclareSymbolFont{stixsymbols}{LS1}{stixscr}{m}{n}
\SetSymbolFont{stixsymbols}{bold}{LS1}{stixscr}{b}{n}
\DeclareMathSymbol{\kay}{\mathalpha}{stixsymbols}{"6B}

\begin{document}
  $\kay$ \boldmath$\kay$
\end{document}