Enveloping a set of draw paths located relative to a node into a TikZ object efficiently - latex

Question

Consider a set of draw paths located relative to a node anchor to be reused again and again in the scope of a tikzpicture. Is it possible to envolope the object creation into a macro while passing a node, a node anchor, or the anchor's coordinate as arguments? The code follows below,
\usetikzlibrary{positioning}
\usepackage{tikz}
\begin{tikzpicture}
%General positions
\def\mtHeight{2};
\def\nodexpas{0.7};
\def\seriallength{2};
%Node style
\tikzstyle{naked}=[every node/.style={inner sep=0,outer sep=0,minimum height=0,minimum width=0,node contents={}}];
%Reference nodes
\begin{scope}[every node/.style={draw,double,rounded corners, align = center,fill=white}]
%Next Element node
\node (NE) [anchor=west,outer sep=0] at (\seriallength+\nodexpas,\mtHeight) {\small Next \\ \small Element()};
%Local Stiffness node
\node (LS) [right=\nodexpas of NE.east] {\small Local \\ \small Stiffness};
%Buffer filling node
\node (BF) [right=\nodexpas of LS.east] {\small Buffer \\ \small filling};
\end{scope}
%Object "lock" data;
\def\lockdim{0.35};
\def\lockpasy{\lockdim/2};
\def\arccorneroffset{\lockdim/10};
\def\lockpasx{\lockdim/2-\arccorneroffset};
\def\arcverticaloffset{\lockdim/3};
\def\lockrelcenter{\lockdim/2+\arcverticaloffset/2+\lockpasx/2};
%First lock
\node[naked] (lock1pos) [left=\nodexpas/2 of NE.west,shape=coordinate,node contents={}];
\draw[fill = gray!50!white] (lock1pos) ++(-\lockdim/2,-\lockdim) rectangle +(\lockdim,\lockdim);
\draw (lock1pos) ++(\lockpasx,0) -- +(0,\arcverticaloffset) arc[start angle = 0, end angle = 180, radius = \lockpasx] -- +(0,-\arcverticaloffset);
%Second Lock
\node[naked] (lock2pos) [left=\nodexpas/2 of LS.west,shape=coordinate,node contents={}];
\draw[fill = gray!50!white] (lock2pos) ++(-\lockdim/2,-\lockdim) rectangle +(\lockdim,\lockdim);
\draw (lock2pos) ++(\lockpasx,0) -- +(0,\arcverticaloffset) arc[start angle = 0, end angle = 180, radius = \lockpasx];
%Third Lock
\node[naked] (lock3pos) [left=\nodexpas/2 of BF.west,shape=coordinate,node contents={}];
\draw[fill = gray!50!white] (lock3pos) ++(-\lockdim/2,-\lockdim) rectangle +(\lockdim,\lockdim);
\draw (lock3pos) ++(\lockpasx,0) -- +(0,\arcverticaloffset) arc[start angle = 0, end angle = 180, radius = \lockpasx] -- +(0,-\arcverticaloffset);
\end{tikzpicture}
Note that lock 1 and 3 are identical, but lock 2 should have one less line. Hence, is it possible to,
Define this "lock" creation macro with a toggleble boolean for the close (lock 1 and 3) and close(lock 2) variations?
Define two objects, one for an open and other for the closed locks?
If macro turns out to not be the best solution, is there another way of automatizing this procedure via, preferably, TikZ or another extension?
I'm trying to make this work using tikzset command, but without much progress. I can't figure a way to pass the node as an argument or to extract the coordinate of a node's anchor. I've checked pgf tools out, but, if possible, I'd rather solve this using only TikZ. In case TikZ alone lacks sufficient tools, pgf tools or another extension should work fine.