In my view, for boats without a rigid vang, the topping lift has two primary functions: 1) it supports the boom while sails are furled and while hoisting the main, and 2) it is a key line providing sail control (really boom control) during reefing evolutions.
It is this second function that is most important to me. I have a traditional slab reefing setup and I reef from a position on the cabin top at the mast. During reefing it is important to be able to tighten the topping lift to support the boom prior to releasing the halyard and then, after the reef is set, release the boom and trim the main.
I have seen topping lifts as described in the previous post (block at the masthead) though this places the block in a difficult place to maintain or inspect. The advantage of this arrangement is that the cleat for the topping lift is at the mast and is easily handled when adjusting the main halyard.
On my 323 the old/original topping lift system consisted of a wire rope fixed at the masthead and which extended to within about 2 feet of the boom in its normal position. The wire rope was extended to the boom by adding a fixed length of line and a snap shackle that attached to a twisted D shackle at the aft end of the boom. This was NOT a good arrangement for reefing. With the topping lift fixed at the masthead a better arrangement uses a turning block (or a bullet block on a swivel) placed at the aft end of the boom with the line cleated forward on the boom. In this manner the topping lift can be adjusted from a position on the cabin top aft of the mast.
There are variations to these two arrangements that include a line routed through the interior of the boom to an exit point just aft of the gooseneck. Also, when utilizing a topping lift fixed at the masthead, a line can be run from the aft end of the boom, to a block at the lower end of the topping lift, back to a turning block at the boom, then forward along the boom to a cleat. This doubles the purchase on the topping lift. This is hardly necessary on the 323 and it also adds a block at the lower end of the topping lift line, which could become a hazard if the line along the boom ever parted.
I currently employ a trapeze cleat in a rather unorthodox arrangement that utilizes the topping lift fixed at the masthead and a line extending through the trapeze cleat to a shackle that attaches to the aft end of the boom. This allows me to completely detach the topping lift from the boom and secure it to the backstay while sailing. I cannot recommend this arrangement because the topping lift control is from the cockpit while the reefing function is from the cabin top. I plan to change it on my boat as soon as I have the time and money to replace the wire rope topping lift with a low-stretch synthetic line, a turning block at the aft end of the boom, and a cleat forward on the boom.
