module strand(j,len){  // strand counter, length
      le=len/10;
      ysep=sep*j;
        ty=ysep+10+yty[j];
        by=ysep+yby[j];     
    
         b=[0,ty];
          c=[for (j=[1:1:(le/2)-1]) [j*di,ysep+10+rands(-2,2,1)[0] ]];
           d= [(le/2)*di,ty];
            e=[(le/2)*di,by];
             f=[for (j=[(le/2)+2:1:le])[(le-j+1)*di,ysep++rands(-2,2,1)[0]]];
              g=[0,by] ;     
       p=concat([b],c,[d],[e],f,[g]); 
         
      polygon(p);
 
}

module block(ns,len){ // number of strands, length
  for (j=[0:1:ns-1])
        strand(j,len);
}

di = 20; // y distance between points (needs fixing at 20)
//ns = 15; // number of strands
maxs = 50; //maximum number of strands (for start and ends)
sep = 18; // strand separation
//len = 40;  // length of strand

yby= rands(-2,2,maxs);  //generate start and end r points
yty= rands(-2,2,maxs);

// play with blocks
for (j=[2:1:10])
translate([j*100,0,0])block(22,100);
block(20,100);

translate([200,395,0])block(15,900);