# How can I fix the small gaps in \hhline and make it (and double vertical lines) intransparent to particular vertical (horizontal) lines?

Take a look at this table:

\documentclass[12pt,a4paper]{report}
\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage[activate={true,nocompatibility},final,tracking=false,kerning=true,spacing=true,factor=1100,stretch=10,shrink=10]{microtype}
\DisableLigatures[f]{encoding = T1}
\usepackage{color}
\usepackage{etoolbox}
\microtypecontext{spacing=nonfrench}
\usepackage{geometry}
\usepackage{multirow}
\usepackage{hhline}
\usepackage{float}
\geometry{
left=2cm,
right=2cm,
top=2cm,
bottom=2cm,
bindingoffset=0mm
}
\begin{document}
\begin{table}[H]
\centering
\begin{tabular}{c|c||cc|cc|cc}
& $\boldsymbol{(1 - \tau_0) i}$ & \multicolumn{2}{c|}{\multirow{2}{*}{$\boldsymbol{\alpha = 0{,}01}$}} & \multicolumn{2}{c|}{\multirow{2}{*}{$\boldsymbol{\alpha = 0{,}02}$}} & \multicolumn{2}{c}{\multirow{2}{*}{$\boldsymbol{\alpha = 0{,}03}$}} \\
$\boldsymbol{i}$ & $\boldsymbol{=}$ & \multicolumn{2}{c|}{} & \multicolumn{2}{c|}{} & \multicolumn{2}{c}{}\\
& $\boldsymbol{0{,}25}$ & $\boldsymbol{n = 0{,}04}$ & $\boldsymbol{n = 0{,}05}$ & $\boldsymbol{n = 0{,}04}$ & $\boldsymbol{n = 0{,}05}$ & $\boldsymbol{n = 0{,}04}$ & $\boldsymbol{n = 0{,}05}$\\ \hhline{=|=#==|==|==}
$0{,}05$ & $0{,}0375$ & $\infty$ & $\infty$ & $\infty$ & $\infty$ & $\infty$ & $\infty$\\ \hline
$0{,}06$ & $0{,}0450$ & $42{,}16$ & $\infty$ & $51{,}35$ & $\infty$ & $52{,}85$ & $\infty$\\ \hline
$0{,}07$ & $0{,}0525$ & $23{,}11$ & $47{,}03$ & $32{,}30$ & $57{,}24$ & $33{,}79$ & $58{,}78$\\ \hline
$0{,}08$ & $0{,}0600$ & $14{,}69$ & $21{,}97$ & $23{,}89$ & $32{,}19$ & $25{,}38$ & $33{,}37$
\end{tabular}
\end{table}
\end{document}


Using \usepackage{hhline} enables me to draw a double horizontal line which is transparent for vertical lines:

It even enables double vertical lines with the help of #:

But taking a closer look reveals that \hhline is comprised of several small lines which leave gaps inbetween:

I would like to get rid of these gaps, but I don’t know how. This is no solution for me.

Furthermore, I would like the double horizontal and vertical line to interrupt all intersecting lines. Also, I would like to deactivate # so that neither the double horizontal nor the double vertical line can interrupt each other. This would/should look like this:

 ___| |___
___   ___
| |


 ___|_|___

You can use :: to get an open crossing instead of # however the lines are made by drawing a line in each cell, so they are separate lines which start and stop at the same point. Some PDF viewers may show a small gap due to rounding to pixel boundaries, some are better at avoiding that.
It would, in principle, be possible to merge adjacent - or = segments and make a single \leaders run across the span, however that would require quite a lot of changes to the package.