Left Right A B C D E B A E C D A - UST - upper steering lines B - Lower control line(s) C - LST - lower steering lines D - BRK - tog line E - Lower control line toggle setting Allow at least 6 inches extra for finger-trapping Mark Brake-set loop Toggle mark A Square Canopy—Control Line Replacement Procedure Disassembly Reassembly •  Applicable products: Square main canopies •  Description: Replacement of the control line  assemblies on square main canopies •  Authorized repairmen: FAA Senior or Master  Parachute Rigger •  Materials: E thread—color to match; suspension  line—type and color to match. Most control line  assemblies utilize two or more types of line: one for  the upper control lines and a stronger one for the lower  control lines. •  Machines: 308 zigzag—medium duty 7–11 SPI and  1 inch × 42 stitch bar tack (optional) •  Equipment: Scissors, seam ripper, marking pencil,  6-inch ruler, tape measure, and small safety pins with  marker flags 2.  Using a finger-trapping needle or wire, finger-trap a  loop at the center of each of the lines so the result is a  line with a loop at the center with two legs extending  from it.  [Figure B]  The eye of the loop should be no  more than .25 inch with the fingertrapped portion 1 inch  long. Bar tack or zigzag the finger-trapped section. 1.  After measuring the control lines, remove them from  one side only. Leave the other side for a reference to  check the new lines against both for measurements  and construction. 1.  Determine how many upper control lines there are  on the canopy. Four is the most common and this  procedure uses this number for the example. With four  upper control lines, there are really two continuous  lines forming the assembly. Each pair of upper lines  is folded in the middle to form two legs of the upper  assembly. Each line is therefore measured at twice  the A dimension plus 12 inches. If the upper control  lines have different lengths, make sure to use the  longest measurement to determine the cut length for  A.  [Figure A] 3.  There are two types of lower control line configurations:  a continuous line and a non-continuous line. The  continuous line is one piece with a brake loop  finger-trapped into it at the proper location. The non- continuous line consists of two pieces that form the  upper lower and lower lower control line, as well as  the brake loop. The continuous line configuration is  found primarily on the older generation main canopies  and on many of today’s reserve canopies. The non- continuous configuration is found on most of the  modern main canopies due to the ease of replacement  because of wear.  7-33 Some manufacturers provide line measurements for their  canopies in their owner’s manuals. If so, the rigger should  thoroughly measure the control line assembly and compare  the measurements against those in the manual. Over time and  use, the control lines have a tendency to stretch and change  dimensions. At the same time, the rigger needs to compare  the right and left side assemblies against each other for any  differences. It is not uncommon for the left and right control  lines to be different lengths, having been changed to remove a  slight turn or change the opening characteristics.  Figure A  is  a sample chart that the rigger can fill in to document the  various dimensions needed to repair or replace control lines.