Here is Board Game Geek's description of the game:

This is an old Parker Brothers sequence card game. The deck consists of three Block cards and five suits - A, B, C, D, and E. The suit cards run from 1 to 11 (there is no A4 or A9). The entire deck is dealt out to the players. The player to the left of the dealer starts by laying down any card from his hand. The player who holds the next higher card in the suit (regardless of where they sit at the table) must follow, laying the card down on the table (D4 followed by D5 for example). Then whoever holds the next higher card plays that, thus continuing in sequence (unless blocked) until the high card of the suit is reached.

Whoever plays the high card (or blocks) gains the Lead, and starts a new sequence by playing any suit card from his hand, thus getting rid of two of his cards. If you have a Block card and you wish to "block" a sequence, you play the next card in the sequence paired with the Block card. You then Lead the next sequence, thus getting rid of three of your cards. As the hand continues, natural blocks occur due to players leading with cards in the middle of suits. The player who plays the A5 or the A10 card wins an immediate 5 or 10 points respectively.

When a player plays his last card, the hand ends, and that player receives 1 point for every card left in the other player's hands. He also scores 5 or 10 points if the A5 or the A10 cards remain unplayed. A player still holding a Block card loses 5 points as a penalty. The first player to score 100 points wins.