This product is thinner than water and seeps into virtually any crack. Once applied it will seal any leak. Apply to the area where you suspect a leak. Let it set for about 20 minutes. If it gets absorbed add some more because it has found an area that needs to be sealed. Finally wipe off the excess. If there was a leak it should be gone. This is for very small leaks that your eye cannot see. For larger leaks use Dicor lap sealant. I have used Capt. Tolleys several times and it works very well. click on the link to buy it. http://www.westmarine.com/buy/captain-tolleys--crack-cure-sealant-2-oz--243990?cm_mmc=PS-_-Google-_-Dynamic+Search+Ads-_-DSA+-+All+Webpages&adpos=1t2&creative=82268438164&device=c&matchtype=b&network=g&gclid=CPOup5aT28gCFRMjgQod1xIHWQ