Rodent Guard Device for Mooring Lines – 37 cm PVC Disc

This rodent repellent device, commonly known as a “rat guard” disc, is a proven solution used for decades in maritime settings (often seen on mooring lines of ships) and now available for use on smaller vessels. The principle is simple yet effective: the disc, about 37 cm in diameter, is attached around the rope connecting your boat to the dock or anchor. If a rat or mouse tries to run along the rope, it encounters the disc – due to the disc’s smooth, broad surface and large diameter, the rodent cannot get past it or around it, often falling into the water or retreating. Thus, your boat stays protected from unwelcome “stowaways” that could otherwise cause damage (gnawed wires, contamination, spread of disease).

Construction & Material: The device is made of durable PVC designed to withstand the elements – it won’t crack easily and it contains UV inhibitors to prevent aging and brittleness under the sun. The PVC material is light enough not to stress your line, yet robust enough to handle impacts (for instance, if the disc knocks against the pier in waves). The shape of the disc is either conical or double-cone – essentially like an inverted funnel that can wobble on the rope. The size is optimized – the ~37 cm diameter has been proven to deter even large rats, while the center opening accommodates various rope thicknesses. The outer edge may feature a lip or flare that further prevents rodents from getting a grip.

Installation: The disc typically comes in two halves that clamp around the rope. This means you can install it at any time without untying or feeding the entire rope through – a huge convenience since mooring lines are often under tension or difficult to re-run. Once you snap or screw the two halves together around the line, the disc stays in place at the desired position. It’s recommended to position it a few feet/meters out from the dock (midway on the rope between boat and shore), so that the rodent has no foothold from either side. For complete protection, if your boat is secured by multiple lines (e.g. two at the stern and two at the bow), it’s wise to put a guard on each line, because one open “path” is enough for a crafty critter.

Usage & Benefits: This device is especially valuable if you keep your boat in marinas near urban areas, fishing piers, or river docks, where rat populations can be high. Rodents are attracted to boats because there is often food on board, soft materials for nesting, or simply shelter. A single overnight visit from a rat can cause havoc – chewed electrical wires, soiled cabins, and a fright for those on board. By placing rat guard discs on all lines connecting your boat to land (stern and bow lines), you create an inexpensive yet effective barrier. Unlike ultrasonic repellents or poisons – which may not be 100% reliable and require power or replenishment – the physical barrier method doesn’t fail: it either stops the rodent or it doesn’t, and in this case – it does stop them successfully.

The rodent guard disk is useful for both permanent installation and occasional use. For instance, if you’re docking overnight in a new location, you can quickly snap these devices on when tying up – they’re compact to store on board when not in use. For boats in long-term slips (marinas), many owners leave them on full-time, especially in warmer months when pest activity is high. Maintenance is minimal – just check the clamps or screws periodically to ensure they’re secure, and rinse off any salt or dirt buildup. The PVC construction has no metal parts to rust, so the device can last you for many seasons.