Here's another option using decorations to produce the two requested styles:
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}
\def\MarkLt{6pt}
\def\MarkSep{3pt}
\tikzset{
TwoMarks/.style={
postaction={decorate,
decoration={
markings,
mark=at position #1 with
{
\begin{scope}[xslant=0.2]
\draw[line width=\MarkSep,white,-] (0pt,-\MarkLt) -- (0pt,\MarkLt) ;
\draw[-] (-0.5\MarkSep,-\MarkLt) -- (-0.5\MarkSep,\MarkLt) ;
\draw[-] (0.5\MarkSep,-\MarkLt) -- (0.5\MarkSep,\MarkLt) ;
\end{scope}
}
}
}
},
TwoMarks/.default={0.5},
OneMark/.style={
postaction={decorate,
decoration={
markings,
mark=at position #1 with
{
\draw[-] (0,-\MarkLt) -- (0,\MarkLt) ;
}
}
}
},
OneMark/.default={0.5}
}
\begin{document}
\begin{tikzpicture}[>=latex]
\draw[TwoMarks,->] (0,0) -- (0,2);
\draw[TwoMarks] (0,0) -- (2,0);
\draw[TwoMarks,->] (0,0) -- (2,2);
\draw[OneMark,<-] (2,0) -- (2,2);
\draw[OneMark] (0,2) -- (2,2);
\draw[TwoMarks=0.25,->] (3,2) -- ++(2,0);
\draw[TwoMarks,->] (3,1) -- ++(2,0);
\draw[TwoMarks=0.75,->] (3,0) -- ++(2,0);
\draw[OneMark=0.25,->] (6,2) -- ++(2,0);
\draw[OneMark,->] (6,1) -- ++(2,0);
\draw[OneMark=0.75,->] (6,0) -- ++(2,0);
\end{tikzpicture}
\end{document}

Features:
Using \MarkLt and \MarkSep one chan change the line length and separation between lines for the double mark.
By default, the decorations are placed in the middle of the path, but using TwoMarks=<value> or OneMark=<value>, the position can be changed.