Tips for Safely Blocking a Boat 

Blocking a boat is straightforward in principle, but should be done very diligently in practice. 

These handy tips will help ensure both you and your boat are safe during the blocking process.

• Always use proper boat stands (also known as jack stands or poppet stands) when blocking a boat, as makeshift stands may not support the weight of the vessel, which could lead to damage to it or bodily harm to you. 
• Never lift a boat using boat stands alone, as neither the boat nor the stands are designed for that, and doing so will damage the hull. When blocking a boat, the weight of the boat is taken by keel blocks placed under the centerline of the keel, while the jack stands prevent the boat from tipping over.

• The top of a keel block should be made of wood at least 18 inches long, with a cross section of at least 4" x 4" for boats up to 30 feet; at least 6" x 6" for boats up to 40 ft.; and at least 8" x 8" for boats over 40 feet.
• Below the wood support, a keel block can be built up using concrete blocks. Make sure the blocks are actual concrete blocks and not cinder blocks, as concrete blocks are denser and more suitable for carrying a boat's weight.
• Only block a boat on level ground that is relatively solid and compacted. Never block a boat on a slope or loose ground.

• Wooden bases (plywood for example) may be used to spread the load from jack stands, and prevent them from moving or sinking into the ground.
• A boat's user manual will often tell you where keel blocks and jack stands should be placed. If you don't have a user manual or blocking instructions, place keel blocks and jack stands where bulkheads reinforce the hull.
• A minimum of two keel blocks should be used (one under the stern, one toward the bow) with additional keel blocks for each 10 feet of boat length: A 20 ft boat should have two keel blocks, a 30 ft boat should have three keel blocks, etc.

• A minimum of four boat stands should be used (two at the stern, two toward the bow), with additional jack stands for each 15 feet of boat length: A boat 30 ft or under should have four jack stands; a boat 45 ft or under should have six jack stands, etc.
• Take your time when working under the boat, as even a small boat could prove heavy enough to severely injure or kill you if it were to fall.

These tips will be helpful the next time you have to block your boat. However, if you’re not sure how to do it correctly, ask a local boatyard, or get in touch with your boat’s manufacturer for additional help.