mjhjmtu

The following code

documentclass[tikz,border=1mm]standalone
 usepackagetikz
 begindocument 
 newcommandopacity0.6 
 begintikzpicture 
 draw[xshift=1cm,fill=gray,draw=black,opacity=opacity] 
 (0,0) -- (3,3) -- (3.2,3) -- (0.2,0) -- (0,0);
 draw[xshift=2cm,fill=gray,draw=black,opacity=opacity] 
 (0,0) -- (2,2) -- (2.2,2) -- (0.2,0) -- (0,0); 
 draw[xshift=3cm,fill=gray,draw=black,opacity=opacity] 
 (0,0) -- (1,1) -- (1.2,1) -- (0.2,0) -- (0,0); 
 endtikzpicture 
 enddocument

produces the following output:

How can I connect the edges of the rectangles with a line? I don't want to use coordinates (draw (0,0) -- (2,2)) but rather something like

draw (rectangle1.north east) -- (rectangle2.north west).

It would also be great if there is a solution like:

draw (A1)(0,0) -- (B1)(1,1) -- (C1)(1.2,1) -- (D1)(0.2,0) -- (E1)(0,0);
draw (A2)(0,0) -- (B2)(1,1) -- (C2)(1.2,1) -- (D2)(0.2,0) -- (E2)(0,0);
draw (A1) -- (C2)

Something like this ?

documentclass[tikz,border=1mm]standalone
 usepackagetikz
 begindocument 
 newcommandopacity0.6 
 begintikzpicture 
 draw[xshift=1cm,fill=gray,draw=black,opacity=opacity] 
 (0,0)coordinate(A1) -- (3,3)coordinate(A2) -- (3.2,3)coordinate(A3) -- (0.2,0) coordinate(A4) -- cycle;
 draw[xshift=2cm,fill=gray,draw=black,opacity=opacity] 
 (0,0)coordinate(B1) -- (2,2)coordinate(B2) -- (2.2,2)coordinate(B3) -- (0.2,0)coordinate(B4) -- cycle; 
 draw[xshift=3cm,fill=gray,draw=black,opacity=opacity] 
 (0,0)coordinate(C1) -- (1,1) coordinate(C2)-- (1.2,1)coordinate(C3) -- (0.2,0)coordinate(C4) -- cycle; 

 draw(A4)--(B1);
 draw(B4)--(C1);
 draw(A3)--(B3)--(C3);

 endtikzpicture 
 enddocument

Update using a foreach loop:

documentclass[tikz,border=1mm]standalone
 usepackagetikz
 begindocument 
 newcommandopacity0.6 
 begintikzpicture

 foreach xs/p/x in1/A/3,2/B/2,3/C/1
 draw[xshift=xs cm,fill=gray,draw=black,opacity=opacity]
 (0,0)coordinate(p1)
 --(x,x)coordinate(p2)
 --(x+0.2,x)coordinate(p3)
 --(0.2,0)coordinate(p4)
 --cycle;

 draw(A4)--(B1);
 draw(B4)--(C1);
 draw(A3)--(B3)--(C3);

 endtikzpicture 
 enddocument

As far as I understand your post, if two coordinates are given, the full shape is fixed. Your shape is not a rectangle, but a trapezium, and there are predefined shapes available.

documentclass[tikz,border=3.14mm]standalone
usetikzlibraryshapes.geometric
begindocument
begintikzpicture[my trapez/.style=trapezium,%inner xsep=0pt,inner ysep=0pt,
trapezium left angle=135, trapezium right angle=45,rotate=45,
minimum width=#1*sqrt(2)*1cm,minimum height=sqrt(2)*1mm,draw,fill=gray,
 trapezium stretches body,anchor=west]
node[my trapez=3] (L) at (1,0) ;
node[my trapez=2] (M) at (2,0) ;
node[my trapez=1] (R) at (3,0) ;
draw ([xshift=-sqrt(2)*1mm]L.west) -- ([xshift=sqrt(2)*1mm]R.west); 
draw ([xshift=sqrt(2)*1mm]L.east) -- ([xshift=sqrt(2)*1mm]R.east); 
endtikzpicture
enddocument

As you can see, there are two mild problems with this approach:

1. it is nontrivial to control the dimensions precisely, at least for this shape;


2. to specify the position precisely, you need to think a bit. (This is also the case in Zarko's otherwise nice answer.)

Therefore, I'd like to propose a different route, in which you to draw and fill the thing as a decoration, which also lets you name the coordinates.

documentclass[tikz,border=1mm]standalone
usetikzlibrarydecorations.pathreplacing
tikzsettrapez width/.initial=0.2cm,
my trapez/.style=decorate,decoration=
show path construction,
lineto code=filldraw
(tikzinputsegmentfirst) coordinate(#1-south west) 
-- (tikzinputsegmentlast) coordinate(#1-north west)
-- ([xshift=pgfkeysvalueof/tikz/trapez width]tikzinputsegmentlast)
coordinate(#1-north east)
-- ([xshift=pgfkeysvalueof/tikz/trapez width]tikzinputsegmentfirst)
coordinate(#1-south east) -- cycle;


begindocument 
 begintikzpicture
 beginscope[fill=gray,opacity=0.6]
 draw[my trapez=L] (1,0) -- (4,3);
 draw[my trapez=M] (2,0) -- (4,2);
 draw[my trapez=R] (3,0) -- (4,1);
 endscope
 draw (L-north east) -- (R-north east)
 (L-south west) -- (R-south east);
 endtikzpicture 
enddocument

Now you really only need to specify two coordinates, which will become precisely named coordinates.

let me elaborate my comment:

• for shapes, which you draw as you show in your mwe, this is not possible


• those shapes haven't defined names nor anchors.


• 
  

  you can do this by use of coordinates for each shape corner, but this can result in quite complex code. for example for the first shape:

  
  
  

  draw[myshape] (0,0) coordinate (A1) -- 
   (3,3) coordinate (A2) -- 
   (3.2,3) coordinate (A3) -- 
   (0.2,0) coordinate (A4) -- cycle; 
  

  
  
  

  and than draw for example

  
  
  

  draw (A1) -- (A3);
  

  
  


• 
  

  a way to simplify this code extension can be use of the small pictures: pic (for details about it see chapter 18 Pics: Small Pictures on Paths in Tikz & PGF manual, v 3.0.1a, page 251):

  
  
  

  documentclass[tikz,border=3mm]standalone
  
  begindocument
   begintikzpicture[
  pics/myshape/.style = code= % definition of your shape
   draw[fill=gray,opacity=opacity]
   ( 0.0,0) coordinate (-1) -- ++ % south west
   ( 0.2,0) coordinate (-2) -- ++ % south east
   (#1,#1) coordinate (-3) -- ++ % north east, coordinate is determined by parameter #1
   (-0.2,0) coordinate (-4) -- % north west
   cycle;
   ]
  defopacity0.6
  pic (A) [above right] at (0,0) myshape=3; % "3" is parameter which define size of shape
  pic (B) [above right] at (1,0) myshape=2;
  pic (C) [above right] at (2,0) myshape=1;
  draw[very thin, red, densely dashed]
   (A-3) -- (B-3); % instead of draw (rectangle1.north east) -- (rectangle2.north west).
   endtikzpicture
  enddocument
  

  
  



• for coordinates name you can select more meaningful names. for example instead of -1 may be more appropriate -sw, which can associate you on "south west", etc.